Relevant part from the build log:

running build_ext
building '_ctypes' extension
gcc -pthread -Wno-unused-result -Wsign-compare -DDYNAMIC_ANNOTATIONS_ENABLED=1 -DNDEBUG -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -D_GNU_SOURCE -fPIC -fwrapv -fPIC -I/usr/include -I. -IObjects -IInclude -IPython -I/usr/local/include -I/builddir/build/BUILD/Python-3.6.4/Include -I/builddir/build/BUILD/Python-3.6.4/build/optimized -c /builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/_ctypes.c -o build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/_ctypes.o
gcc -pthread -Wno-unused-result -Wsign-compare -DDYNAMIC_ANNOTATIONS_ENABLED=1 -DNDEBUG -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -D_GNU_SOURCE -fPIC -fwrapv -fPIC -I/usr/include -I. -IObjects -IInclude -IPython -I/usr/local/include -I/builddir/build/BUILD/Python-3.6.4/Include -I/builddir/build/BUILD/Python-3.6.4/build/optimized -c /builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callbacks.c -o build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callbacks.o
gcc -pthread -Wno-unused-result -Wsign-compare -DDYNAMIC_ANNOTATIONS_ENABLED=1 -DNDEBUG -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -D_GNU_SOURCE -fPIC -fwrapv -fPIC -I/usr/include -I. -IObjects -IInclude -IPython -I/usr/local/include -I/builddir/build/BUILD/Python-3.6.4/Include -I/builddir/build/BUILD/Python-3.6.4/build/optimized -c /builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callproc.c -o build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callproc.o
gcc -pthread -Wno-unused-result -Wsign-compare -DDYNAMIC_ANNOTATIONS_ENABLED=1 -DNDEBUG -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -D_GNU_SOURCE -fPIC -fwrapv -fPIC -I/usr/include -I. -IObjects -IInclude -IPython -I/usr/local/include -I/builddir/build/BUILD/Python-3.6.4/Include -I/builddir/build/BUILD/Python-3.6.4/build/optimized -c /builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/stgdict.c -o build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/stgdict.o
gcc -pthread -Wno-unused-result -Wsign-compare -DDYNAMIC_ANNOTATIONS_ENABLED=1 -DNDEBUG -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -D_GNU_SOURCE -fPIC -fwrapv -fPIC -I/usr/include -I. -IObjects -IInclude -IPython -I/usr/local/include -I/builddir/build/BUILD/Python-3.6.4/Include -I/builddir/build/BUILD/Python-3.6.4/build/optimized -c /builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/cfield.c -o build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/cfield.o
gcc -pthread -shared -Wl,-z,relro -Wl,-z,defs -specs=/usr/lib/rpm/redhat/redhat-hardened-ld -g build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/_ctypes.o build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callbacks.o build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callproc.o build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/stgdict.o build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/cfield.o -L. -L/usr/local/lib64 -lffi -lpython3.6m -o build/lib.linux-x86_64-3.6/_ctypes.cpython-36m-x86_64-linux-gnu.so
build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/_ctypes.o: In function `PyCFuncPtr_FromDll':
/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/_ctypes.c:3391: undefined reference to `dlsym'
/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/_ctypes.c:3399: undefined reference to `dlerror'
build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/_ctypes.o: In function `CDataType_in_dll':
/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/_ctypes.c:675: undefined reference to `dlsym'
/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/_ctypes.c:683: undefined reference to `dlerror'
build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callproc.o: In function `py_dl_open':
/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callproc.c:1329: undefined reference to `dlopen'
/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callproc.c:1332: undefined reference to `dlerror'
build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callproc.o: In function `py_dl_sym':
/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callproc.c:1366: undefined reference to `dlsym'
/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callproc.c:1369: undefined reference to `dlerror'
build/temp.linux-x86_64-3.6/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callproc.o: In function `py_dl_close':
/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callproc.c:1348: undefined reference to `dlclose'
/builddir/build/BUILD/Python-3.6.4/Modules/_ctypes/callproc.c:1350: undefined reference to `dlerror'
collect2: error: ld returned 1 exit status
The following modules found by detect_modules() in setup.py, have been
built by the Makefile instead, as configured by the Setup files:
atexit                pwd                   time               
Failed to build these modules:
_ctypes