Scons: Use full pathnames for nacl-gcc etc. instead of relying on PATH
Scons: Use full pathnames for nacl-gcc etc. instead of relying on PATH

This makes it easier to copy-and-paste the nacl-gcc invocations that
Scons prints in order to debug what the compiler/linker is doing,
e.g. to add -S to see the assembly code or to add -Wl,-M to see the
linker map.

BUG=none
TEST=run on trybots

Review URL: http://codereview.chromium.org/3605002

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@3389 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

nacl-webkit/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client