Fix lld standalone build

lld/ELF/OutputSections.cpp includes llvm/Config/config.h for
LLVM_ENABLE_ZLIB definition, but llvm/Config/config.h doesn't exist in
standalone build.

To fix this, this patch moves LLVM_ENABLE_ZLIB from config.h to
llvm-config.h and updates OutputSections.cpp to include llvm-config.h
instead of config.h

Reviewed By: MaskRay, mgorny

Differential Revision: https://reviews.llvm.org/D119058

lld/ELF/OutputSections.cpp

@@ -16,7 +16,7 @@
 #include "lld/Common/Memory.h"
 #include "lld/Common/Strings.h"
 #include "llvm/BinaryFormat/Dwarf.h"
-#include "llvm/Config/config.h" // LLVM_ENABLE_ZLIB
+#include "llvm/Config/llvm-config.h" // LLVM_ENABLE_ZLIB
 #include "llvm/Support/MD5.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/Parallel.h"

llvm/include/llvm/Config/config.h.cmake

@@ -300,9 +300,6 @@
 /* Doesn't use `cmakedefine` because it is allowed to be empty. */
 #define LLVM_DEFAULT_TARGET_TRIPLE "${LLVM_DEFAULT_TARGET_TRIPLE}"
 
-/* Define if zlib compression is available */
-#cmakedefine01 LLVM_ENABLE_ZLIB
-
 /* Define if overriding target triple is enabled */
 #cmakedefine LLVM_TARGET_TRIPLE_ENV "${LLVM_TARGET_TRIPLE_ENV}"
 

llvm/include/llvm/Config/llvm-config.h.cmake

@@ -88,6 +88,9 @@
 /* Define if we have curl and want to use it */
 #cmakedefine LLVM_ENABLE_CURL ${LLVM_ENABLE_CURL}
 
+/* Define if zlib compression is available */
+#cmakedefine01 LLVM_ENABLE_ZLIB
+
 /* Define if LLVM was built with a dependency to the libtensorflow dynamic library */
 #cmakedefine LLVM_HAVE_TF_API