Fix public issue #6: Add a --with-gflags for disabling gflags autodetection

and using a manually given setting (use/don't use) instead.

R=csilvers
DELTA=16  (13 added, 0 deleted, 3 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=991


git-svn-id: https://snappy.googlecode.com/svn/trunk@9 03e5f5b5-db94-4691-08a0-1a8bf15f6143

configure.ac

@@ -21,10 +21,23 @@ AC_CHECK_HEADERS([stdint.h stddef.h])
 AC_CHECK_FUNC([mmap])
 
 GTEST_LIB_CHECK([], [true], [true # Ignore; we can live without it.])
-PKG_CHECK_MODULES([gflags], [libgflags],
+
+AC_ARG_WITH([gflags],
+  [AS_HELP_STRING(
+    [--with-gflags],
+    [use Google Flags package to enhance the unit test @<:@default=check@:>@])],
+    [],
+    [with_gflags=check])
+
+if test "x$with_gflags" != "xno"; then
+  PKG_CHECK_MODULES(
+    [gflags],
+    [libgflags],
     [AC_DEFINE([HAVE_GFLAGS], [1], [Use the gflags package for command-line parsing.])],
-    [true # Ignore; we can live without it.]
-)
+    [if test "x$with_gflags" != "xcheck"; then
+      AC_MSG_FAILURE([--with-gflags was given, but test for gflags failed])
+    fi])
+fi
 
 # See if we have __builtin_expect.
 # TODO: Use AC_CACHE.