configure: Disable LLVM asserts by default

configure

@@ -533,7 +533,7 @@ opt optimize-cxx 1 "build optimized C++ code"
 opt optimize-llvm 1 "build optimized LLVM"
 opt optimize-tests 1 "build tests with optimizations"
 opt libcpp 1 "build with llvm with libc++ instead of libstdc++ when using clang"
-opt llvm-assertions 1 "build LLVM with assertions"
+opt llvm-assertions 0 "build LLVM with assertions"
 opt debug-assertions 0 "build with debugging assertions"
 opt fast-make 0 "use .gitmodules as timestamp for submodule deps"
 opt ccache 0 "invoke gcc/clang via ccache to reuse object files between builds"
@@ -1170,7 +1170,7 @@ do
             LLVM_DBG_OPTS="--enable-optimized"
             LLVM_INST_DIR=$LLVM_BUILD_DIR/Release
         fi
-        if [ ! -z "$CFG_DISABLE_LLVM_ASSERTIONS" ]
+        if [ -z "$CFG_ENABLE_LLVM_ASSERTIONS" ]
         then
             LLVM_ASSERTION_OPTS="--disable-assertions"
         else