diff --git a/build.zig b/build.zig
index 65e0840d82..bef3b3b58f 100644
--- a/build.zig
+++ b/build.zig
@@ -91,20 +91,6 @@ pub fn build(b: *Builder) !void {
     exe.addBuildOption(bool, "have_llvm", enable_llvm);
     if (enable_llvm) {
         const cmake_cfg = if (static_llvm) null else findAndParseConfigH(b, config_h_path_option);
-
-        const exe_cflags = [_][]const u8{
-            "-std=c++14",
-            "-D__STDC_CONSTANT_MACROS",
-            "-D__STDC_FORMAT_MACROS",
-            "-D__STDC_LIMIT_MACROS",
-            "-D_GNU_SOURCE",
-            "-fvisibility-inlines-hidden",
-            "-fno-exceptions",
-            "-fno-rtti",
-            "-Werror=type-limits",
-            "-Wno-missing-braces",
-            "-Wno-comment",
-        };
         if (is_stage1) {
             exe.addIncludeDir("src");
             exe.addIncludeDir("deps/SoftFloat-3e/source/include");
@@ -123,6 +109,19 @@ pub fn build(b: *Builder) !void {
             softfloat.addCSourceFiles(&softfloat_sources, &[_][]const u8{ "-std=c99", "-O3" });
             exe.linkLibrary(softfloat);
 
+            const exe_cflags = [_][]const u8{
+                "-std=c++14",
+                "-D__STDC_CONSTANT_MACROS",
+                "-D__STDC_FORMAT_MACROS",
+                "-D__STDC_LIMIT_MACROS",
+                "-D_GNU_SOURCE",
+                "-fvisibility-inlines-hidden",
+                "-fno-exceptions",
+                "-fno-rtti",
+                "-Werror=type-limits",
+                "-Wno-missing-braces",
+                "-Wno-comment",
+            };
             exe.addCSourceFiles(&stage1_sources, &exe_cflags);
             exe.addCSourceFiles(&optimized_c_sources, &[_][]const u8{ "-std=c99", "-O3" });
             if (cmake_cfg == null) {
@@ -206,12 +205,6 @@ pub fn build(b: *Builder) !void {
                 exe.linkSystemLibrary(lib_name);
             }
 
-            // We need this because otherwise zig_clang_cc1_main.cpp ends up pulling
-            // in a dependency on llvm::cfg::Update<llvm::BasicBlock*>::dump() which is
-            // unavailable when LLVM is compiled in Release mode.
-            const zig_cpp_cflags = exe_cflags ++ [_][]const u8{"-DNDEBUG=1"};
-            exe.addCSourceFiles(&zig_cpp_sources, &zig_cpp_cflags);
-
             // This means we rely on clang-or-zig-built LLVM, Clang, LLD libraries.
             exe.linkSystemLibrary("c++");
 
diff --git a/src/zig_clang.h b/src/zig_clang.h
index 169fbcedfb..32879062ae 100644
--- a/src/zig_clang.h
+++ b/src/zig_clang.h
@@ -8,32 +8,14 @@
 #ifndef ZIG_ZIG_CLANG_H
 #define ZIG_ZIG_CLANG_H
 
+#include "stage1/stage2.h"
 #include <inttypes.h>
 #include <stdbool.h>
-#include <stddef.h>
-
-#ifdef __cplusplus
-#define ZIG_EXTERN_C extern "C"
-#else
-#define ZIG_EXTERN_C
-#endif
 
 // ATTENTION: If you modify this file, be sure to update the corresponding
 // extern function declarations in the self-hosted compiler file
 // src/clang.zig.
 
-// ABI warning
-struct Stage2ErrorMsg {
-    const char *filename_ptr; // can be null
-    size_t filename_len;
-    const char *msg_ptr;
-    size_t msg_len;
-    const char *source; // valid until the ASTUnit is freed. can be null
-    unsigned line; // 0 based
-    unsigned column; // 0 based
-    unsigned offset; // byte offset into source
-};
-
 struct ZigClangSourceLocation {
     unsigned ID;
 };