I'm trying to install python 2.6 using pyenv but when doing pyenv install 2.6.9I get the following:

checking MACHDEP... darwin
checking EXTRAPLATDIR... $(PLATMACDIRS)
checking machine type as reported by uname -m... x86_64
checking for --without-gcc... no
checking for gcc... gcc
checking whether the C compiler works... no
configure: error: in `/var/folders/r9/771hsm9931sd81ppz31384p80000gn/T/python-build.20150213191018.2121/Python-2.6.9':
configure: error: C compiler cannot create executables

I've installed Xcode 4.6.3 and installed Command Line Tools as info.
Cheers,
Ch
Actually I found the problem. The problem was with the ld: library not found for -lgcc_ext.10.5
The gcc version given by Xcode 4.6.3 on Mac OS X Lion is 4.6.

I installed the new gcc via homebrew, brew install gcc.
I symlink my gcc to gcc-4.9 by doing ln -s /usr/local/bin/gcc /usr/local/bin/gcc-4.9.
make sure the that in your PATH /usr/local/bin is before /usr/bin ).
To a ls -l 'which gcc' to check that gcc is associated to the 4.9 version. Once this is done, the library is found and python 2.6 can be installed using pyenv.
checking whether the C compiler works... no when installing python 2.6 (mac os x lion)