Add platform to cache key

Even though caches are not shared across platforms by default, it seems
that they may not be namespaced as we are getting warnings that keys
already exist.

src/common.mts

@@ -1,3 +1,5 @@
 import { join } from "node:path";
 
 export const archive = join("trimja-cache", "ninjafiles.tar.gz");
+
+export const cachePrefix = `TRIMJA-${process.platform}-`;

src/main.m.mts

@@ -6,7 +6,7 @@ import { promisify } from "node:util";
 import { join } from "node:path";
 import { execFile as execFileCallback } from "node:child_process";
 import { appendFile, writeFile } from "node:fs/promises";
-import { archive } from "./common.mjs";
+import { archive, cachePrefix } from "./common.mjs";
 const execFile = promisify(execFileCallback);
 
 function getPlatformVars(version: string): {
@@ -77,15 +77,17 @@ try {
     });
 
     info("Getting affected files");
-    const matchedCache = await restoreCache([archive], "TRIMJA-", ["TRIMJA-"]);
+    const matchedCache = await restoreCache([archive], cachePrefix, [
+      cachePrefix,
+    ]);
     if (matchedCache === undefined) {
       info("No cache found, skipping trimja");
       return;
     }
 
     info("Extracting ninja files");
     await extractTar(archive, builddir);
-    const hash = matchedCache.slice("TRIMJA-".length);
+    const hash = matchedCache.slice(cachePrefix.length);
 
     info(`Attempting to fetch ${hash}...`);
     try {

src/post.m.mts

@@ -4,7 +4,7 @@ import { exec } from "@actions/exec";
 import { join } from "node:path";
 import { existsSync } from "node:fs";
 import { mkdir } from "node:fs/promises";
-import { archive } from "./common.mjs";
+import { archive, cachePrefix } from "./common.mjs";
 
 try {
   (async () => {
@@ -27,7 +27,7 @@ try {
     info(`Creating ${archive}`);
     await exec("tar", ["-czvf", archive, "-C", builddir, ...files]);
 
-    const key = `TRIMJA-${HASH}`;
+    const key = `${cachePrefix}${HASH}`;
     info(`Saving cache '${key}'`);
     await saveCache([archive], key);
   })();