Use commit_id.py on Windows, and handle missing git.

This allows us to delete the Windows batch file.

Changes the commit_id script to take the working directory so that it
can be called from a different working directory than the angle
repository is in.

Renames the generated commit header to angle_commit.h. This is being
written to the shared generated code directory for the entire build,
and "commit.h" is insufficiently unique.

BUG=angle:669

Change-Id: I35e80411a7e8ba1e02ce3f6a4fc54ed4dbc918f3
Reviewed-on: https://chromium-review.googlesource.com/202048
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libGLESv2/ProgramBinary.cpp b/src/libGLESv2/ProgramBinary.cpp
index 8525ffb..e3ffa47 100644
--- a/src/libGLESv2/ProgramBinary.cpp
+++ b/src/libGLESv2/ProgramBinary.cpp
@@ -1018,6 +1018,9 @@
 
 bool ProgramBinary::load(InfoLog &infoLog, const void *binary, GLsizei length)
 {
+#ifdef ANGLE_DISABLE_PROGRAM_BINARY_LOAD
+    return false;
+#else
     BinaryInputStream stream(binary, length);
 
     int format = stream.readInt<int>();
@@ -1260,6 +1263,7 @@
     initializeUniformStorage();
 
     return true;
+#endif // #ifdef ANGLE_DISABLE_PROGRAM_BINARY_LOAD
 }
 
 bool ProgramBinary::save(void* binary, GLsizei bufSize, GLsizei *length)