[NaCl SDK] Check for valid CONFIG parameter to Makefile.

native_client_sdk/src/tools/common.mk

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 #
 # GNU Make based build file.  For details on GNU Make see:
 #   http://www.gnu.org/software/make/manual/make.html
 #
 
 #
@@ skipping 94 matching lines @@
 # build the debug configuration by default instead.
 #
 ifneq (,$(findstring debug,$(MAKECMDGOALS)))
 CONFIG ?= Debug
 else
 CONFIG ?= Release
 endif
 
 
 #
+# Verify we selected a valid configuration for this example.
+#
+VALID_CONFIGS ?= Debug Release
+ifeq (,$(findstring $(CONFIG),$(VALID_CONFIGS)))
+  $(warning Availbile choices are: $(VALID_CONFIGS))
+  $(error Can not use CONFIG=$(CONFIG) on this example.)
+endif
+
+
+#
 # Note for Windows:
 #   The GCC and LLVM toolchains (include the version of Make.exe that comes
 # with the SDK) expect and are capable of dealing with the '/' seperator.
 # For this reason, the tools in the SDK, including Makefiles and build scripts
 # have a preference for POSIX style command-line arguments.
 #
 # Keep in mind however that the shell is responsible for command-line escaping,
 # globbing, and variable expansion, so those may change based on which shell
 # is used.  For Cygwin shells this can include automatic and incorrect expansion
 # of response files (files starting with '@').
@@ skipping 384 matching lines @@
 # uppercase aliases (for backward compatibility)
 .PHONY: CHECK_FOR_CHROME DEBUG LAUNCH RUN
 CHECK_FOR_CHROME: check_for_chrome
 DEBUG: debug
 LAUNCH: run
 RUN: run
 
 endif  # TOOLCHAIN is valid...
 
 endif  # TOOLCHAIN=all