Add a warning about headers in Android builds

dist-build/android-build.sh

@@ -33,6 +33,12 @@ export CC=${CC:-"${HOST_COMPILER}-clang"}
 
 rm -rf "${TOOLCHAIN_DIR}" "${PREFIX}"
 
+echo
+echo "Warnings related to headers being present but not usable are due to functions"
+echo "that didn't exist in the specified minimum API version level."
+echo "They can be safely ignored."
+echo
+
 echo
 if [ "$NDK_PLATFORM" != "$NDK_PLATFORM_COMPAT" ]; then
   echo "Building for platform [${NDK_PLATFORM}], retaining compatibility with platform [${NDK_PLATFORM_COMPAT}]"