Prune the list of third_party symlinks

.gitignore

Index: .gitignore
diff --git a/.gitignore b/.gitignore
index d26d64709080231707cd7489d3a34a5e550c4488..89d168fba80bdfbbf1e8ac32c1e59422e0a4f7e3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -22,57 +22,17 @@ pin-log.txt
 /third_party/asan
 /third_party/ashmem
 /third_party/binutils
-/third_party/boringssl
 /third_party/BUILD.gn
-/third_party/clang_format
-/third_party/class-dump
-/third_party/colorama
-/third_party/cygwin
-/third_party/directxsdk
 /third_party/drmemory
-/third_party/expat
-/third_party/gaeunit
 /third_party/gflags/src
-/third_party/icu
 /third_party/instrumented_libraries
-/third_party/ijar
-/third_party/jsoncpp
-/third_party/jsr-305
-/third_party/junit
-/third_party/junit-jar
-/third_party/libc++
-/third_party/libc++abi
-/third_party/libevent
-/third_party/libjingle
 /third_party/libjpeg
 /third_party/libjpeg_turbo
-/third_party/libsrtp
-/third_party/libvpx
-/third_party/libxml
-/third_party/libudev
-/third_party/libyuv
 /third_party/llvm
 /third_party/llvm-build
 /third_party/lss
-/third_party/mockito
-/third_party/modp_b64
-/third_party/nss
-/third_party/oauth2
-/third_party/ocmock
-/third_party/openmax_dl
-/third_party/opus
-/third_party/proguard
 /third_party/protobuf
-/third_party/requests
-/third_party/robolectric
-/third_party/sqlite
-/third_party/syzygy
-/third_party/usrsctp
-/third_party/valgrind
-/third_party/WebKit
-/third_party/winsdk_samples/src
 /third_party/yasm
-/third_party/zlib
 /tools/android
 /tools/clang
 /tools/find_depot_tools.py