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Of course there't no single set of options, that much is
true of any platform.
However, I've provided one set of options that does work. 
It's clear to me that little testing is being done building
Python for the 64-bit ABI mode of targets such as IRIX,
Solaris, and other platforms using the vendor compilers. 
(maybe gcc works, but I can't use gcc...)  In the case of
the other platforms, there are comments in the README that
are helpful to those of us that need to build a 64-bit
Python interpreter for embedding in 64-bit applications. 
Several Python 2.3 versions I tried fail to pass on build
flags to some of the module builds, proving that nobody
tested this in the past.  2.4.2c1 works, but you have to set
all of these environment variables to get it to work. 
Anyway, as far as the options I selected:  You could choose
-O but the Sun compilers prefer -xO3 (some old versions
whine at you if you use -O).  I chose -mt for thread safety,
which is already documented in the Python README.   Simply
setting CC to "cc -xarch=native64" worked way back in Python
2.2, but fails with 2.3.x and 2.4.x.  If you try that on
2.4.2c1 and use the configure flags below,
setenv CC "cc -xarch=native64"
./configure --without-cxx --without-gcc
You can see that the build scripts have already lost the
-xarch=native64 in the first couple of compiles:
cc -c  -DNDEBUG -O -I. -I./Include  -DPy_BUILD_CORE -o
Parser/metagrammar.o Parser/metagrammar.c
cc -c  -DNDEBUG -O -I. -I./Include  -DPy_BUILD_CORE -o
Parser/firstsets.o Parser/firstsets.c
cc -c  -DNDEBUG -O -I. -I./Include  -DPy_BUILD_CORE -o
Parser/grammar.o Parser/grammar.c

If I eliminate the "--without-gcc" flag to configure, the
build does work
by setting CC to "cc -xarch=native64".  I don't know why it
breaks when one adds --without-gcc, but it'd be nice if the
docs cleared this up.  
With Python 2.2, adding --without-gcc did not break the build.
This is exactly the problem with the current state of the
build system and docs.  I don't mind the fact that it's a
little hokey to get the build done, but it'd be nice if the
docs contained the facts needed to do this without a
trial-and-error based search of the configuration space to
avoid the bugs in the build system.