fix(ci): sccache wrapper + incremental=false for correct caching

- Add sccache wrapper that unsets CARGO_INCREMENTAL (sccache 0.14.0
  refuses to work when that env var is present, even if =0)
- Remove rustc-wrapper from .cargo/config.toml (use RUSTC_WRAPPER env in CI)
- Set [profile.dev] incremental = false to avoid sccache 'prohibited' error
- DEV-DEPENDENCIES.sh now installs sccache 0.14.0 + wrapper correctly
- CI workflow: unset CARGO_INCREMENTAL env (let sccache wrapper handle it)

Tested on alm-ci: 50% cache hit rate on rebuild after target/ removal.

.cargo/config.toml

@@ -1,5 +1,4 @@
 [build]
-rustc-wrapper = "sccache"
 jobs = 6
 
 [target.x86_64-unknown-linux-gnu]

.forgejo/workflows/botserver.yaml

@@ -16,7 +16,6 @@ jobs:
     runs-on: gbo
     env:
       RUSTC_WRAPPER: sccache
-      CARGO_INCREMENTAL: "1"
       PATH: "/home/gbuser/.cargo/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/sbin:/bin"
     steps:
       - name: Setup

Cargo.toml

@@ -249,7 +249,7 @@ opt-level = "s"
 
 [profile.dev]
 debug = 1
-incremental = true
+incremental = false
 codegen-units = 32
 opt-level = 0
 

DEV-DEPENDENCIES.sh

@@ -33,16 +33,23 @@ install_sccache() {
   fi
   if [ "$CURRENT_VER" = "$WANT_VER" ]; then
     echo "sccache $WANT_VER already installed"
-    return
+  else
+    echo "Upgrading sccache from ${CURRENT_VER:-none} to $WANT_VER..."
+    rm -f /usr/local/bin/sccache /usr/local/bin/sccache-dist
+    ARCH=$(uname -m)
+    curl -L "https://github.com/mozilla/sccache/releases/download/v${WANT_VER}/sccache-v${WANT_VER}-${ARCH}-unknown-linux-musl.tar.gz" -o /tmp/sccache.tar.gz
+    tar -xzf /tmp/sccache.tar.gz -C /tmp
+    cp "/tmp/sccache-v${WANT_VER}-${ARCH}-unknown-linux-musl/sccache" /usr/local/bin/sccache.real
+    chmod +x /usr/local/bin/sccache.real
+    rm -rf /tmp/sccache*
   fi
-  echo "Upgrading sccache from ${CURRENT_VER:-none} to $WANT_VER..."
-  rm -f /usr/local/bin/sccache /usr/local/bin/sccache-dist
-  ARCH=$(uname -m)
-  curl -L "https://github.com/mozilla/sccache/releases/download/v${WANT_VER}/sccache-v${WANT_VER}-${ARCH}-unknown-linux-musl.tar.gz" -o /tmp/sccache.tar.gz
-  tar -xzf /tmp/sccache.tar.gz -C /tmp
-  cp "/tmp/sccache-v${WANT_VER}-${ARCH}-unknown-linux-musl/sccache" /usr/local/bin/sccache
+  # Install wrapper that unsets CARGO_INCREMENTAL before calling sccache.real
+  cat > /usr/local/bin/sccache << 'EOF'
+#!/bin/bash
+unset CARGO_INCREMENTAL
+exec /usr/local/bin/sccache.real "$@"
+EOF
   chmod +x /usr/local/bin/sccache
-  rm -rf /tmp/sccache*
   sccache --version
 }
 
@@ -77,11 +84,8 @@ jobs = -1
 [target.x86_64-unknown-linux-gnu]
 linker = "clang"
 rustflags = ["-C", "link-arg=-fuse-ld=mold"]
-
-[env]
-RUSTC_WRAPPER = "sccache"
 CARGOCONF
-    echo "Created .cargo/config.toml with mold + sccache"
+    echo "Created .cargo/config.toml with mold"
   else
     echo ".cargo/config.toml already exists, skipping"
   fi