Revert "[CMake] Simplify CMake handling for zlib"

This quietly disabled use of zlib on Windows even when building with
-DLLVM_ENABLE_ZLIB=FORCE_ON.

> Rather than handling zlib handling manually, use find_package from CMake
> to find zlib properly. Use this to normalize the LLVM_ENABLE_ZLIB,
> HAVE_ZLIB, HAVE_ZLIB_H. Furthermore, require zlib if LLVM_ENABLE_ZLIB is
> set to YES, which requires the distributor to explicitly select whether
> zlib is enabled or not. This simplifies the CMake handling and usage in
> the rest of the tooling.
>
> This is a reland of abb0075 with all followup changes and fixes that
> should address issues that were reported in PR44780.
>
> Differential Revision: https://reviews.llvm.org/D79219

This reverts commit 10b1b4a231a485f1711d576e6131f6755e008abe and follow-ups
64d99cc6abed78c00a2a7863b02ce54911a5264f and
f9fec0447e12da9e8cf4b628f6d45f4941e7d182.

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/Support/Compression.cpp b/llvm/lib/Support/Compression.cpp
index b8c77cf..27d92f0 100644
--- a/llvm/lib/Support/Compression.cpp
+++ b/llvm/lib/Support/Compression.cpp
@@ -17,13 +17,13 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
-#if LLVM_ENABLE_ZLIB
+#if LLVM_ENABLE_ZLIB == 1 && HAVE_ZLIB_H
 #include <zlib.h>
 #endif
 
 using namespace llvm;
 
-#if LLVM_ENABLE_ZLIB
+#if LLVM_ENABLE_ZLIB == 1 && HAVE_LIBZ
 static Error createError(StringRef Err) {
   return make_error<StringError>(Err, inconvertibleErrorCode());
 }