gn build: Fix Python 3 write_vcsrevision script compatibility
gn build: Fix Python 3 write_vcsrevision script compatibility

Trivial fix: decode was not called for all subprocess.check_output calls.

Commited on behalf of Andrew Boyarshin

Differential Revision: https://reviews.llvm.org/D57505



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@353168 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm