[gn build] Fix cosmetic bug in write_cmake_config.py
[gn build] Fix cosmetic bug in write_cmake_config.py

Before, #cmakedefine FOO resulted in #define FOO  with a trailing space if FOO
was set to something truthy. Make it so that it's just #define FOO without a
trailing space.

No functional difference.

Differential Revision: https://reviews.llvm.org/D55172


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@348107 91177308-0d34-0410-b5e6-96231b3b80d8

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