chore: remove CARGO_TARGET_DIR override, add build.rs duplication comment

CARGO_TARGET_DIR=target/musl was only needed for cloud cache key
isolation. Cross already outputs to target/<triple>/.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: maxholman

.github/workflows/pr.yml

@@ -53,7 +53,6 @@ jobs:
         if: runner.environment != 'self-hosted'
         with:
           shared-key: musl
-          workspaces: . -> target/musl
 
       - name: Install cross
         run: |
@@ -70,7 +69,7 @@ jobs:
         run: docker build -t wallhack-cross:x86_64-unknown-linux-musl -f Dockerfile.cross-musl .
 
       - name: Test (musl — primary)
-        run: CARGO_TARGET_DIR=target/musl cross test --release --target x86_64-unknown-linux-musl
+        run: cross test --release --target x86_64-unknown-linux-musl
 
   build-musl:
     needs: [test-musl]
@@ -85,7 +84,6 @@ jobs:
         if: runner.environment != 'self-hosted'
         with:
           shared-key: musl
-          workspaces: . -> target/musl
 
       - name: Install cross
         run: |
@@ -102,14 +100,14 @@ jobs:
         run: docker build -t wallhack-cross:x86_64-unknown-linux-musl -f Dockerfile.cross-musl .
 
       - name: Build slim (musl — primary)
-        run: CARGO_TARGET_DIR=target/musl cross build --release --target x86_64-unknown-linux-musl -p wallhack-cli --no-default-features --features slim
+        run: cross build --release --target x86_64-unknown-linux-musl -p wallhack-cli --no-default-features --features slim
 
       - name: Check slim binary size (musl — primary)
         run: ./bench/check_bloat.sh --no-build --only=slim-musl
         continue-on-error: true
 
       - name: Build default (musl — primary)
-        run: CARGO_TARGET_DIR=target/musl cross build --release --target x86_64-unknown-linux-musl -p wallhack-cli
+        run: cross build --release --target x86_64-unknown-linux-musl -p wallhack-cli
 
       - name: Check default binary size (musl — primary)
         run: ./bench/check_bloat.sh --no-build --only=default-musl

crates/cli/build.rs

@@ -1,3 +1,5 @@
+// NOTE: This WallhackBuildEnv impl is duplicated in crates/mcp/build.rs.
+// build.rs files cannot share code via library crates.
 use std::collections::BTreeMap;
 
 use vergen_gitcl::{

crates/mcp/build.rs

@@ -1,3 +1,5 @@
+// NOTE: This WallhackBuildEnv impl is duplicated in crates/cli/build.rs.
+// build.rs files cannot share code via library crates.
 use std::collections::BTreeMap;
 
 use vergen_gitcl::{