Bug 1576751 - set LD_LIBRARY_PATH during Android builds; r=glandium

We need this for host binaries to work correctly in the case where the
clang we're using is linking against a newer version of, say,
`libstdc++` than is on the system.

Differential Revision: https://phabricator.services.mozilla.com/D43529

--HG--
extra : moz-landing-system : lando

mobile/android/config/mozconfigs/common

@@ -30,6 +30,9 @@ if [ -z "$NO_NDK" -a -z "$USE_ARTIFACT" ]; then
     CC="$MOZ_FETCHES_DIR/clang/bin/clang"
     CXX="$MOZ_FETCHES_DIR/clang/bin/clang++"
     ac_add_options --with-android-ndk="$MOZ_FETCHES_DIR/android-ndk"
+    # Make sure that any host binaries we build use whatever libraries clang
+    # linked against, rather than what's on the system.
+    mk_add_options "export LD_LIBRARY_PATH=$MOZ_FETCHES_DIR/clang/lib"
     # Enable static analysis plugin
     export ENABLE_CLANG_PLUGIN=1
 fi