Also detect the CXX_target enviroment vairiable for compiler version

The ninja's cross compile mode still uses CXX_target as the target compiler
which needs to be detected before the host one.

This CL might be reverted once the ninja use CXX as target compiler.

BUG=


Review URL: https://chromiumcodereview.appspot.com/10837005

git-svn-id: http://src.chromium.org/svn/trunk/src/build@150300 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

compiler_version.py

@@ -33,21 +33,42 @@ def GetVersion(compiler):
     print >> sys.stderr, e
     return ""
 
-def main():
-  # Check if CXX environment variable exists and
-  # if it does use that compiler.
-  cxx = os.getenv("CXX", None)
+def GetVersionFromEnvironment(compiler_env):
+  """ Returns the version of compiler
+
+  If the compiler was set by the given environment variable and exists,
+  return its version, otherwise None is returned.
+  """
+  cxx = os.getenv(compiler_env, None)
   if cxx:
-    cxxversion = GetVersion(cxx)
-    if cxxversion != "":
-      print cxxversion
-      return 0
-  else:
-    # Otherwise we check the g++ version.
-    gccversion = GetVersion("g++")
-    if gccversion != "":
-      print gccversion
-      return 0
+    cxx_version = GetVersion(cxx)
+    if cxx_version != "":
+      return cxx_version
+  return None
+
+def main():
+  # Check if CXX_target or CXX environment variable exists an if it does use
+  # that compiler.
+  # TODO: Fix ninja (see http://crbug.com/140900) instead and remove this code
+  # In ninja's cross compile mode, the CXX_target is target compiler, while
+  # the CXX is host. The CXX_target needs be checked first, though the target
+  # and host compiler have different version, there seems no issue to use the
+  # target compiler's version number as gcc_version in Android.
+  cxx_version = GetVersionFromEnvironment("CXX_target")
+  if cxx_version:
+    print cxx_version
+    return 0
+
+  cxx_version = GetVersionFromEnvironment("CXX")
+  if cxx_version:
+    print cxx_version
+    return 0
+
+  # Otherwise we check the g++ version.
+  gccversion = GetVersion("g++")
+  if gccversion != "":
+    print gccversion
+    return 0
 
   return 1