Make the option of building using the host clang the default

I am committing this as a workaround until we fix the ASAN bot.

Author: nadavrot

utils/build-script-impl

@@ -86,7 +86,7 @@ KNOWN_SETTINGS=(
     enable-ubsan                ""               "enable Undefined Behavior Sanitizer"
     cmake                       ""               "path to the cmake binary"
     distcc                      ""               "use distcc in pump mode"
-    build-runtime-with-host-compiler   ""        "use the host c++ compiler to build everything"
+    build-runtime-with-host-compiler   "1"       "use the host c++ compiler to build everything"
     user-config-args            ""               "User-supplied arguments to cmake when used to do configuration"
     cmake-generator             "Unix Makefiles" "kind of build system to generate; see output of 'cmake --help' for choices"
     verbose-build               ""               "print the commands executed during the build"