[third_party] add jdk/current to .gitignore

Bug: 693079
Change-Id: Ib103e0e4d53d3f7d072971780ef9dd07d64cdc1d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1844513
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Auto-Submit: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Yun Liu <yliuyliu@google.com>
Cr-Commit-Position: refs/heads/master@{#703199}

third_party/.gitignore

@@ -117,6 +117,7 @@
 /javax_inject/lib/
 /jacoco/lib/
 /javalang/src/
+/jdk/current
 /jsoncpp/source
 /jsr-305/src
 /junit/src