Don't restrip already stripped binaries.

[ 45% 15/33] //prebuilts/misc/gdbserver:gdbserver strip gdbserver [arm]
prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.9/bin/arm-linux-androideabi-nm: prebuilts/misc/gdbserver/android-arm/gdbserver: no symbols
[ 51% 17/33] //prebuilts/misc/gdbserver:gdbserver strip gdbserver64
prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/bin/aarch64-linux-android-nm: prebuilts/misc/gdbserver/android-arm64/gdbserver64: no symbols

Test: Builds with fewer diagnostics. ;)
Change-Id: Ie90aa515f849a04cfba01c9e7522f6623a220bd9
diff --git a/gdbserver/Android.bp b/gdbserver/Android.bp
index e57681f..8e9c86d 100644
--- a/gdbserver/Android.bp
+++ b/gdbserver/Android.bp
@@ -8,6 +8,11 @@
         },
     },
 
+    // These are already stripped, and restripping them just issues diagnostics.
+    strip: {
+        none: true,
+    },
+
     target: {
         android_arm: {
             srcs: ["android-arm/gdbserver"],