Partially revert r145157 to quiet an unhappy buildbot.

Removing that buildbot would be a better solution, but this is at least
a temporary workaround.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145160 91177308-0d34-0410-b5e6-96231b3b80d8

Makefile

@@ -76,6 +76,14 @@ ifeq ($(MAKECMDGOALS),install-clang)
   NO_INSTALL = 1
 endif
 
+ifeq ($(MAKECMDGOALS),install-clang-c)
+  DIRS := tools/clang/tools/driver tools/clang/lib/Headers \
+          tools/clang/tools/libclang tools/clang/tools/c-index-test \
+         tools/clang/include/clang-c
+  OPTIONAL_DIRS :=
+  NO_INSTALL = 1
+endif
+
 ifeq ($(MAKECMDGOALS),clang-only)
   DIRS := $(filter-out tools docs unittests, $(DIRS)) \
           tools/clang tools/lto
@@ -163,6 +171,7 @@ clang-only: all
 tools-only: all
 libs-only: all
 install-clang: install
+install-clang-c: install
 install-libs: install
 
 # If SHOW_DIAGNOSTICS is enabled, clear the diagnostics file first.