Explicitly add the include path for android_filesystem_config.h

android_filesystem_config.h is found since system/core/include is on
the include path for all projects and contains a symlink to the real
android_filesystem_config.h.  This is fragile and the below bug seeks
to remove this symlink and have users correctly depend on
libcutils_headers.

In bionic, libcutils_headers header library cannot be used due to
cyclic dependencies, so it gets the actual include path instead, which
is less bad than depending on the build system injecting the for all
modules.

Bug: 165825252
Test: build
Change-Id: Id43bdea9553b1174ceb3efc2a3ed505888619c62

libc/Android.bp

@@ -62,6 +62,8 @@ cc_defaults {
     cppflags: [],
     include_dirs: [
         "bionic/libc/async_safe/include",
+        // For android_filesystem_config.h.
+        "system/core/libcutils/include",
     ],
 
     header_libs: [

tests/Android.bp

@@ -44,6 +44,7 @@ cc_defaults {
         // For glibc.
         "-D__STDC_LIMIT_MACROS",
     ],
+    header_libs: ["libcutils_headers"],
     // Ensure that the tests exercise shadow call stack support and
     // the hint space PAC/BTI instructions.
     arch: {