Use thumb versions of external libraries with ARMv7.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index b80fa16a684dcda2b2c925923b406cff2c9932f0..c8b13283a55adfeb78ba95752450a1b19589a3aa 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -483,7 +483,11 @@ config("runtime_library") {
       "-isystem" + rebase_path("$android_stlport_root/stlport",
                                root_build_dir)
     ]
-    lib_dirs += [ "$android_stlport_root/libs/$android_app_abi" ]
+    if (arm_use_thumb) {
+      lib_dirs += [ "$android_stlport_root/libs/$android_app_abi/thumb" ]
+    } else {
+      lib_dirs += [ "$android_stlport_root/libs/$android_app_abi" ]
+    }
 
     if (component_mode == "shared_library") {
       libs += [ "stlport_shared" ]