[gn build] Add build file for clang/lib/Basic and dependencies, 2nd try

Adds a build file for clang-tblgen and an action for running it, and uses that
to process all the .td files in include/clang/Basic.

Also adds an action to write include/clang/Config/config.h and
include/clang/Basic/Version.inc.

Differential Revision: https://reviews.llvm.org/D55847

(The previous commit of this contained unrelated changes, so I reverted the
whole previous commit and I'm now landing only what I intended to land.)

llvm-svn: 349679

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/utils/gn/secondary/clang/lib/ARCMigrate/enable.gni b/llvm/utils/gn/secondary/clang/lib/ARCMigrate/enable.gni
new file mode 100644
index 00000000000..7a7a42edbfd
--- /dev/null
+++ b/llvm/utils/gn/secondary/clang/lib/ARCMigrate/enable.gni
@@ -0,0 +1,4 @@
+declare_args() {
+  # Whether to include the arc migrate tool in the clang binary.
+  clang_enable_arcmt = true
+}