Add breadcrumbs to cmake flags (#900)

Fixes flutter/flutter#155942

Author: reidbaker

build/config/compiler/BUILD.gn

@@ -391,6 +391,12 @@ config("compiler") {
     # to say that it does. Define them here instead.
     defines += [ "HAVE_SYS_UIO_H" ]
 
+    # When Android requires new flags consider also editing the flags in 
+    # the following locations. 
+    # Framework plugin_ffi template: packages/flutter_tools/templates/plugin_ffi/src.tmpl/CMakeLists.txt.tmpl
+    # Example PR: https://github.com/flutter/flutter/pull/155508
+    # Dart Lang JNI package: pkgs/jni/src/CMakeLists.txt 
+    # Example PR: https://github.com/dart-lang/native/pull/1615 
     ldflags += [
       "-Wl,--no-undefined",
       "-Wl,--exclude-libs,ALL",