Allow strip program to be overridden
Allow strip program to be overridden

Through the STRIP environment variable. This is sometimes necessary when
cross-compiling, and is consistent with how gyp allows e.g. CXX to be set
to override the C++ compiler used. The name STRIP was chosen as autotools
also uses it to override its auto-detection.

mafintosh/prebuild,mafintosh/prebuild,mafintosh/prebuild