diff -r 92b3ce7ca95c Makefile.pre.in
--- a/Makefile.pre.in	Sat Jul 30 11:36:32 2016 +0200
+++ b/Makefile.pre.in	Sat Jul 30 17:52:13 2016 +0200
@@ -224,6 +224,7 @@
 
 cross_compiling=@cross_compiling@
 PYTHON_FOR_GEN=@PYTHON_FOR_GEN@
+PY_BUILD_ENVIRON=@PY_BUILD_ENVIRON@
 PYTHON_FOR_BUILD=@PYTHON_FOR_BUILD@
 _PYTHON_HOST_PLATFORM=@_PYTHON_HOST_PLATFORM@
 BUILD_GNU_TYPE=	@build@
@@ -566,14 +567,14 @@
 # (depends on python having already been built)
 .PHONY=clinic
 clinic: $(BUILDPYTHON)
-	$(RUNSHARED) $(PYTHON_FOR_BUILD) ./Tools/clinic/clinic.py --make
+	$(RUNSHARED) $(PY_BUILD_ENVIRON) $(PYTHON_FOR_BUILD) ./Tools/clinic/clinic.py --make
 
 # Build the interpreter
 $(BUILDPYTHON):	Programs/python.o $(LIBRARY) $(LDLIBRARY) $(PY3LIBRARY)
 	$(LINKCC) $(PY_LDFLAGS) $(LINKFORSHARED) -o $@ Programs/python.o $(BLDLIBRARY) $(LIBS) $(MODLIBS) $(SYSLIBS) $(LDLAST)
 
 platform: $(BUILDPYTHON) pybuilddir.txt
-	$(RUNSHARED) $(PYTHON_FOR_BUILD) -c 'import sys ; from sysconfig import get_platform ; print("%s-%d.%d" % (get_platform(), *sys.version_info[:2]))' >platform
+	$(RUNSHARED) $(PY_BUILD_ENVIRON) $(PYTHON_FOR_BUILD) -c 'import sys ; from sysconfig import get_platform ; print("%s-%d.%d" % (get_platform(), *sys.version_info[:2]))' >platform
 
 # Create build directory and generate the sysconfig build-time data there.
 # pybuilddir.txt contains the name of the build dir and is used for
@@ -584,7 +585,7 @@
 # or removed in case of failure.
 pybuilddir.txt: $(BUILDPYTHON)
 	@echo "none" > ./pybuilddir.txt
-	$(RUNSHARED) $(PYTHON_FOR_BUILD) -S -m sysconfig --generate-posix-vars ;\
+	$(RUNSHARED) $(PY_BUILD_ENVIRON) $(PYTHON_FOR_BUILD) -S -m sysconfig --generate-posix-vars ;\
 	if test $$? -ne 0 ; then \
 		echo "generate-posix-vars failed" ; \
 		rm -f ./pybuilddir.txt ; \
@@ -606,7 +607,7 @@
 	esac; \
 	$(RUNSHARED) CC='$(CC)' LDSHARED='$(BLDSHARED)' OPT='$(OPT)' \
 		_TCLTK_INCLUDES='$(TCLTK_INCLUDES)' _TCLTK_LIBS='$(TCLTK_LIBS)' \
-		$(PYTHON_FOR_BUILD) $(srcdir)/setup.py $$quiet build
+		$(PY_BUILD_ENVIRON) $(PYTHON_FOR_BUILD) $(srcdir)/setup.py $$quiet build
 
 # Build static library
 # avoid long command lines, same as LIBRARY_OBJS
@@ -1052,7 +1053,7 @@
 			upgrade) ensurepip="--upgrade" ;; \
 			install|*) ensurepip="" ;; \
 		esac; \
-		$(RUNSHARED) $(PYTHON_FOR_BUILD) -m ensurepip \
+		$(RUNSHARED) $(PY_BUILD_ENVIRON) $(PYTHON_FOR_BUILD) -m ensurepip \
 			$$ensurepip --root=$(DESTDIR)/ ; \
 	fi
 
@@ -1062,7 +1063,7 @@
 			upgrade) ensurepip="--altinstall --upgrade" ;; \
 			install|*) ensurepip="--altinstall" ;; \
 		esac; \
-		$(RUNSHARED) $(PYTHON_FOR_BUILD) -m ensurepip \
+		$(RUNSHARED) $(PY_BUILD_ENVIRON) $(PYTHON_FOR_BUILD) -m ensurepip \
 			$$ensurepip --root=$(DESTDIR)/ ; \
 	fi
 
@@ -1457,7 +1458,7 @@
 # Install the dynamically loadable modules
 # This goes into $(exec_prefix)
 sharedinstall: sharedmods
-	$(RUNSHARED) $(PYTHON_FOR_BUILD) $(srcdir)/setup.py install \
+	$(RUNSHARED) $(PY_BUILD_ENVIRON) $(PYTHON_FOR_BUILD) $(srcdir)/setup.py install \
 	   	--prefix=$(prefix) \
 		--install-scripts=$(BINDIR) \
 		--install-platlib=$(DESTSHARED) \
@@ -1541,7 +1542,7 @@
 # This installs a few of the useful scripts in Tools/scripts
 scriptsinstall:
 	SRCDIR=$(srcdir) $(RUNSHARED) \
-	$(PYTHON_FOR_BUILD) $(srcdir)/Tools/scripts/setup.py install \
+	$(PY_BUILD_ENVIRON) $(PYTHON_FOR_BUILD) $(srcdir)/Tools/scripts/setup.py install \
 	--prefix=$(prefix) \
 	--install-scripts=$(BINDIR) \
 	--root=$(DESTDIR)/
diff -r 92b3ce7ca95c configure.ac
--- a/configure.ac	Sat Jul 30 11:36:32 2016 +0200
+++ b/configure.ac	Sat Jul 30 17:52:13 2016 +0200
@@ -79,7 +79,8 @@
 	    AC_MSG_ERROR([python$PACKAGE_VERSION interpreter not found])
 	fi
         AC_MSG_RESULT($interp)
-	PYTHON_FOR_BUILD='_PYTHON_PROJECT_BASE=$(abs_builddir) _PYTHON_HOST_PLATFORM=$(_PYTHON_HOST_PLATFORM) PYTHONPATH=$(shell test -f pybuilddir.txt && echo $(abs_builddir)/`cat pybuilddir.txt`:)$(srcdir)/Lib:$(srcdir)/Lib/$(PLATDIR) '$interp
+	PY_BUILD_ENVIRON='_PYTHON_PROJECT_BASE=$(abs_builddir) _PYTHON_HOST_PLATFORM=$(_PYTHON_HOST_PLATFORM) PYTHONPATH=$(shell test -f pybuilddir.txt && echo $(abs_builddir)/`cat pybuilddir.txt`:)$(srcdir)/Lib:$(srcdir)/Lib/$(PLATDIR)'
+	PYTHON_FOR_BUILD=$interp
     fi
     PGEN_DEPENDENCY=''
 elif test "$cross_compiling" = maybe; then
@@ -88,6 +89,7 @@
     PYTHON_FOR_BUILD='./$(BUILDPYTHON) -E'
     PGEN_DEPENDENCY='$(PGEN)'
 fi
+AC_SUBST(PY_BUILD_ENVIRON)
 AC_SUBST(PYTHON_FOR_BUILD)
 AC_SUBST(PGEN_DEPENDENCY)