diff --git a/src/build/llvmPackages.ts b/src/build/llvmPackages.ts
index 873e798..44cfe44 100644
--- a/src/build/llvmPackages.ts
+++ b/src/build/llvmPackages.ts
@@ -16,6 +16,40 @@ export interface LLVMPackageOverrides {
     spawnOverrides?: (old: SpawnOptions) => SpawnOptions,
 }
 
+/**
+ * Make sysroot options suitable for LLVM build.
+ */
+export function llvmBuildSysroot(prefix: string): LLVMPackageOverrides {
+    return {
+        cmakeDefinitionOverrides: {
+            llvm: {
+                CMAKE_C_COMPILER: path.resolve(prefix, 'usr', 'bin', 'gcc'),
+                CMAKE_CXX_COMPILER: path.resolve(prefix, 'usr', 'bin', 'g++'),
+                CMAKE_SYSROOT: prefix,
+            },
+            libpgmath: {
+                CMAKE_SYSROOT: prefix,
+            },
+            cflang: {
+
+                CMAKE_SYSROOT: prefix,
+            },
+        },
+        spawnOverrides: o => ({
+            ...o,
+            env: {
+                ...o.env,
+                LD_LIBRARY_PATH: [
+                    path.resolve(prefix, 'lib'),
+                    path.resolve(prefix, 'usr', 'lib'),
+                ].join(':')
+            }
+        }),
+
+    };
+}
+
+
 export interface LLVMPackageOptions {
     src: string;
     installPrefix: string;