One of the problems that I see in that LDFLAGS is Makefile variable and
Makefile is part of distribution for posix build systems.
If you set specific LDFLAGS and you want to distribute own python build
user will get you specific settings.
One another environment variable is OPT (if compiler don't accept -R XXX
may be -Wl,-rpath,XXX ?) and we may use it. Also OPT environment
variable is also Makefile variable and user specific settings will go
into distribution too :( .

I quick look into distutils code show that sysconfig.py don't parse
LDFLAGS and append environment variable LDFLAGS as is to the ldshared
variable.
So the first question is why setup.py parse only -L flags instead to
pass variable value as is (aka sysconfig.py).
The second question is why LDFLAGS is a Makefile variable ? 


For now I would like to know if you set on Solaris suitable
LD_RUN_PATH(for the build) and LD_LIBRARY_PATH (when run) did you
succeed to build and run python ?