[MIPS] Do not force clang for mipsel Linux

Fix the MIPS Linux build that was broken by r282266 (and r282246).
Related r282266 review is at https://codereview.chromium.org/382743002

TEST= build Chrome Linux for target_arch=mipsel

Review URL: https://codereview.chromium.org/396243002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@283645 0039d316-1c4b-4281-b951-d872f2087c98

build/common.gypi

@@ -1787,7 +1787,7 @@
         # the class names, so the JNI generator needs to know this.
         'jni_generator_jarjar_file': '../android_webview/build/jarjar-rules.txt',
       }],
-      ['OS=="linux"', {
+      ['OS=="linux" and target_arch!="mipsel"', {
         # TODO(thakis): This is here to measure perf for a while.
         'clang%': 1,
       }],  # OS=="mac"