Build gtest from source rather than using SDK-provided version

ports/glibc-compat/build.sh

Index: ports/glibc-compat/build.sh
diff --git a/ports/glibc-compat/build.sh b/ports/glibc-compat/build.sh
index f6f6d9223d815790fdd27701da3514f1a213a2a7..bfb9c44990082cbf82562880759a25c7441dfcd3 100644
--- a/ports/glibc-compat/build.sh
+++ b/ports/glibc-compat/build.sh
@@ -12,6 +12,7 @@ ConfigureStep() {
   LogExecute rm -rf out
 }
 
+
 BuildStep() {
   if [ "${TOOLCHAIN}" = "emscripten" ]; then
     return
@@ -25,6 +26,7 @@ BuildStep() {
   export LDFLAGS=${NACLPORTS_LDFLAGS}
   export CPPFLAGS=${NACLPORTS_CPPFLAGS}
   export CFLAGS=${NACLPORTS_CFLAGS}
+  export GTEST_DIR=${NACL_PREFIX}/src/gtest
   DefaultBuildStep
 }