[analyzer] Fix out-of-tree only clang build by not relaying on private header

It turned out that the D78704 included a private LLVM header, which is excluded
from the LLVM install target.
I'm substituting that `#include` with the public one by moving the necessary
`#define` into that. There was a discussion about this at D78704 and on the
cfe-dev mailing list.

I'm also placing a note to remind others of this pitfall.

Reviewed By: mgorny

Differential Revision: https://reviews.llvm.org/D84929

clang/unittests/StaticAnalyzer/FalsePositiveRefutationBRVisitorTest.cpp

@@ -16,7 +16,7 @@
 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
 #include "clang/StaticAnalyzer/Frontend/AnalysisConsumer.h"
 #include "clang/StaticAnalyzer/Frontend/CheckerRegistry.h"
-#include "llvm/Config/config.h"
+#include "llvm/Config/llvm-config.h"
 #include "gtest/gtest.h"
 
 // FIXME: Use GTEST_SKIP() instead if GTest is updated to version 1.10.0

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

@@ -1,6 +1,9 @@
 #ifndef CONFIG_H
 #define CONFIG_H
 
+// Include this header only under the llvm source tree.
+// This is a private header.
+
 /* Exported configuration */
 #include "llvm/Config/llvm-config.h"
 
@@ -335,9 +338,6 @@
 /* Whether GlobalISel rule coverage is being collected */
 #cmakedefine01 LLVM_GISEL_COV_ENABLED
 
-/* Define if we have z3 and want to build it */
-#cmakedefine LLVM_WITH_Z3 ${LLVM_WITH_Z3}
-
 /* Define to the default GlobalISel coverage file prefix */
 #cmakedefine LLVM_GISEL_COV_PREFIX "${LLVM_GISEL_COV_PREFIX}"
 

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

@@ -79,6 +79,9 @@
  */
 #cmakedefine01 LLVM_FORCE_ENABLE_STATS
 
+/* Define if we have z3 and want to build it */
+#cmakedefine LLVM_WITH_Z3 ${LLVM_WITH_Z3}
+
 /* Define if LLVM was built with a dependency to the libtensorflow dynamic library */
 #cmakedefine LLVM_HAVE_TF_API