fbcode_builder: fix run_cmake.py to propagate the command return code

Summary:
Update the generated `run_cmake.py` script to use `os.execve()` rather than
`subprocess.call()`, so that it now propagates CMake's return code back to its
caller.

Reviewed By: chadaustin

Differential Revision: D17089206

fbshipit-source-id: e01f05f492ccb842d4967e59fd0bc9a3e59b8a42

build/fbcode_builder/getdeps/builder.py

@@ -200,7 +200,6 @@ from __future__ import absolute_import, division, print_function, unicode_litera
 
 import argparse
 import os
-import subprocess
 
 CMAKE = {cmake!r}
 SRC_DIR = {src_dir!r}
@@ -266,7 +265,8 @@ def main():
 
     cmd_str = " ".join(full_cmd)
     print("Running: %r" % (cmd_str,))
-    subprocess.call(full_cmd, env=env, cwd=BUILD_DIR)
+    os.chdir(BUILD_DIR)
+    os.execve(CMAKE, full_cmd, env)
 
 
 if __name__ == "__main__":