build: Ignore gyp-generated files on android

The android generator for gyp currently doesn't support
--generator-output - this makes embedding node.js as project dependency
difficult for android projects.

Note: the generated files in deps/uv should be ignored in libuv's
.gitignore

.gitignore

@@ -52,6 +52,12 @@ deps/openssl/openssl.props
 deps/openssl/openssl.targets
 deps/openssl/openssl.xml
 
+# generated by gyp on android
+/*.target.mk
+/*.host.mk
+deps/openssl/openssl.target.mk
+deps/zlib/zlib.target.mk
+
 # build/release artifacts
 /*.tar.gz
 /SHASUMS*.txt*