Bug 1471339 - Link with clang_rt.profile-x86_64 library in Linux code coverage builds. r=glandium

--HG--
extra : rebase_source : 390bcc57b8decc423801a7e497be18f8baeadac5

browser/config/mozconfigs/linux64/code-coverage

@@ -13,4 +13,5 @@ ac_add_options --enable-coverage
 
 export CFLAGS="--coverage"
 export CXXFLAGS="--coverage"
-export LDFLAGS="--coverage -L$TOOLTOOL_DIR/gtk3/usr/local/lib"
+export LDFLAGS="--coverage -L$topsrcdir/clang/lib/clang/7.0.0/lib/linux/"
+export LIBS="-lclang_rt.profile-x86_64"