Remove the install-clang-c makefile target.

When I did this before it broke a buildbot that was testing that target, but
we've removed that buildbot now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145519 91177308-0d34-0410-b5e6-96231b3b80d8

Makefile

@@ -76,14 +76,6 @@ 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
@@ -171,7 +163,6 @@ 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.