build: add --with-python option

This adds a new --with-python option to allow configuration of the python binary
for building.  If not specified, $PATH will be searched for common python binary
names (python, python2, python3).  If specified, and the path is not executable,
it will attempt to search $PATH.

Signed-off-by: Saleem Abdulrasool <[email protected]>
Reviewed-by: Eric Christopher <[email protected]>, Daniel Dunbar <[email protected]>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173890 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed