Fix gdb python support for Android platform debugging

GDB with python support looks for specfic set of locations for PYTHONHOME.
Add one more clue to find $ANDROID_BUILD_TOP/prebuilts/python/linux-x86/2.7.5
Note that ANDROID_BUILD_TOP is set by doing usual setup in Android development,
ie.

   . build/envsetup.sh
   lunch ...

Change-Id: I0b4db61aa392bd2c09b29ac224e74465fd19a1d6
1 file changed