GN: add a helper script for running Android builds

gn/BUILD.gn

Index: gn/BUILD.gn
diff --git a/gn/BUILD.gn b/gn/BUILD.gn
index c5db0a96608b0760588e559d24a6a44ac4182f09..fd2d0074c6f9abadeccf65b71206b99fa2147560 100644
--- a/gn/BUILD.gn
+++ b/gn/BUILD.gn
@@ -31,7 +31,6 @@ config("no_rtti") {
 config("default") {
   cflags = [
     "-O1",
-    "-g",
     "-fstrict-aliasing",
     "-fPIC",
     "-fvisibility=hidden",
@@ -57,6 +56,14 @@ config("default") {
   ]
   ldflags = []
 
+  # It's annoying to wait for full debug symbols to push over
+  # to Android devices.  -gline-tables-only is a lot slimmer.
+  if (is_android) {
+    cflags += [ "-gline-tables-only" ]
+  } else {
+    cflags += [ "-g" ]
+  }
+
   if (current_cpu == "arm") {
     cflags += [
       "-march=armv7-a",