diff --git a/src/build/llvmPackages.ts b/src/build/llvmPackages.ts
index f3998c5..873e798 100644
--- a/src/build/llvmPackages.ts
+++ b/src/build/llvmPackages.ts
@@ -6,6 +6,16 @@ import { promisifySpawn } from "lyc/cli";
 import os from "os";
 import { SpawnOptions, spawn } from "child_process";
 
+export interface LLVMPackageOverrides {
+    cmakeDefinitionOverrides?: {
+        llvm?: Object,
+        libpgmath?: Object,
+        cflang?: Object,
+    };
+
+    spawnOverrides?: (old: SpawnOptions) => SpawnOptions,
+}
+
 export interface LLVMPackageOptions {
     src: string;
     installPrefix: string;
@@ -19,39 +29,24 @@ export interface LLVMPackageOptions {
         libpgmath: string;
     };
 
-    /**
-     * Misc toolchain settings for compiling LLVM.
-     */
-    toolchains: {
-        llvm: {
-            CC: string;
-            CXX: string;
-        };
-    };
-
-    cmakeDefinitionOverrides?: {
-        llvm?: Object,
-        libpgmath?: Object,
-        cflang?: Object,
-    };
-
     platform: PackagePlatform;
 };
 
 export function llvmPackages({
     src,
     installPrefix,
-    toolchains,
     platform,
     buildDirs,
     cmakeDefinitionOverrides,
-}: LLVMPackageOptions): PackageTask[] {
+    spawnOverrides,
+}: LLVMPackageOptions & LLVMPackageOverrides): PackageTask[] {
     const rm = "rm";
     const cmake = "cmake";
 
     const llvmVar: LLVMVariable = {
         LLVM_ENABLE_PROJECTS: ["clang", "clang-tools-extra", "lld", "openmp"],
         LLVM_TARGETS_TO_BUILD: ["Sw64"],
+        LLVM_ENABLE_CLASSIC_FLANG: true,
         LIBOMP_ARCH: "Sw64",
         LIBOMP_USE_ITT_NOTIFY: false,
     };
@@ -66,11 +61,11 @@ export function llvmPackages({
         MAKEFLAGS: ["-j", os.cpus().length].join(" "),
     };
 
-    const spawnOptions: SpawnOptions = {
+    const spawnOptions: SpawnOptions = (spawnOverrides || (o => o))({
         stdio: "inherit",
         env,
         cwd: src,
-    };
+    });
 
     const mkBuildPhase = (build: string) => (async () => {
         await promisifySpawn(spawn(cmake, ["--build", build], spawnOptions));
@@ -102,8 +97,6 @@ export function llvmPackages({
                     definitions: variable({
                         ...llvmVar,
                         ...general,
-                        CMAKE_C_COMPILER: toolchains.llvm.CC,
-                        CMAKE_CXX_COMPILER: toolchains.llvm.CXX,
                         ...cmakeDefinitionOverrides?.llvm || {},
                     }),
                     generator: "Ninja",
@@ -156,7 +149,6 @@ export function llvmPackages({
                 // Configure cflang.
                 await promisifySpawn(spawn(cmake, command({
                     definitions: variable({
-                        ...llvmVar,
                         ...general,
                         ...{
                             CMAKE_C_COMPILER: path.join(installPrefix, "bin", "clang"),
@@ -184,4 +176,3 @@ export function llvmPackages({
     return [mkLLVMPackage(), mkLibpgmathPackage(), mkCflangPackage()];
 
 }
-