Revert^2 "Add an explanation to ndk_library."

This reverts commit a27204273d.

Reason for revert: unrelated to breakage

Change-Id: Ic7cb64acd72ee8502e608609c0e197fba6a27bf2

cc/ndk_library.go

@@ -103,8 +103,17 @@ type libraryProperties struct {
 	// https://github.com/android-ndk/ndk/issues/265.
 	Unversioned_until *string
 
-	// Headers presented by this library to the Public API Surface
+	// DO NOT USE THIS
+	// NDK libraries should not export their headers. Headers belonging to NDK
+	// libraries should be added to the NDK with an ndk_headers module.
 	Export_header_libs []string
+
+	// Do not add other export_* properties without consulting with danalbert@.
+	// Consumers of ndk_library modules should emulate the typical NDK build
+	// behavior as closely as possible (that is, all NDK APIs are exposed to
+	// builds via --sysroot). Export behaviors used in Soong will not be present
+	// for app developers as they don't use Soong, and reliance on these export
+	// behaviors can mask issues with the NDK sysroot.
 }
 
 type stubDecorator struct {