update Win/Android toolchain setup after rolling GN

The new GN doesn't like "ar = ar + ...", etc.

CQ_INCLUDE_TRYBOTS=skia.primary:Build-Win-Clang-arm64-Release-Android

Change-Id: Ib131ee367c4af144f8ffb8562fc26b67675e4f45
Reviewed-on: https://skia-review.googlesource.com/5726
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/gn/BUILD.gn b/gn/BUILD.gn
index c71ec3f..88427c0 100644
--- a/gn/BUILD.gn
+++ b/gn/BUILD.gn
@@ -9,13 +9,14 @@
   cxx = "c++"
 
   if (is_android) {
-    ar = "$ndk/toolchains/$ndk_gccdir-4.9/prebuilt/$ndk_host/$ndk_target/bin/ar"
-    cc = "$ndk/toolchains/llvm/prebuilt/$ndk_host/bin/clang"
-    cxx = "$ndk/toolchains/llvm/prebuilt/$ndk_host/bin/clang++"
     if (host_os == "win") {
-      ar = ar + ".exe"
-      cc = cc + ".exe"
-      cxx = cxx + ".exe"
+      ar = "$ndk/toolchains/$ndk_gccdir-4.9/prebuilt/$ndk_host/$ndk_target/bin/ar.exe"
+      cc = "$ndk/toolchains/llvm/prebuilt/$ndk_host/bin/clang.exe"
+      cxx = "$ndk/toolchains/llvm/prebuilt/$ndk_host/bin/clang++.exe"
+    } else {
+      ar = "$ndk/toolchains/$ndk_gccdir-4.9/prebuilt/$ndk_host/$ndk_target/bin/ar"
+      cc = "$ndk/toolchains/llvm/prebuilt/$ndk_host/bin/clang"
+      cxx = "$ndk/toolchains/llvm/prebuilt/$ndk_host/bin/clang++"
     }
   }