[dump] Remove NDEBUG from test to enable dump methods [NFC]

Summary:
Add LLVM_FORCE_ENABLE_DUMP cmake option, and use it along with
LLVM_ENABLE_ASSERTIONS to set LLVM_ENABLE_DUMP.

Remove NDEBUG and only use LLVM_ENABLE_DUMP to enable dump methods.

Move definition of LLVM_ENABLE_DUMP from config.h to llvm-config.h so
it'll be picked up by public headers.

Differential Revision: https://reviews.llvm.org/D38406

llvm-svn: 315590
diff --git a/llvm/lib/Analysis/InlineCost.cpp b/llvm/lib/Analysis/InlineCost.cpp
index b7fe884..411185f 100644
--- a/llvm/lib/Analysis/InlineCost.cpp
+++ b/llvm/lib/Analysis/InlineCost.cpp
@@ -1698,7 +1698,7 @@
   return Cost < std::max(1, Threshold);
 }
 
-#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+#ifdef LLVM_ENABLE_DUMP
 /// \brief Dump stats about this call's analysis.
 LLVM_DUMP_METHOD void CallAnalyzer::dump() {
 #define DEBUG_PRINT_STAT(x) dbgs() << "      " #x ": " << x << "\n"