[LTR] Normalize rustc version

If you have a newer version of rustc installed (or no rustc installed)
you'll end up with config changes for CONFIG_RUSTC_VERSION and
CONFIG_RUSTC_LLVM_VERSION when you run this script.  We use
scripts/dummy-tools to normalize gcc and friends, but that doesn't
apply to rustc.  So create our own dummy rustc that always reports
the same rustc version as in our current config and pass that to
make as RUSTC when running olddefconfig.  That way, local rustc
version does not affect our configs during a rebase.

Author: bmastbergen

lt_rebase.sh

@@ -64,12 +64,34 @@ CIQ_CONFIG_PATH=ciq/configs
 
 CONFIG_LIST=$(ls ${CIQ_CONFIG_PATH}/*.config)
 
+# scripts/dummy-tools doesn't normalize the rustc
+# version.  So create a quick dummy rustc script
+# to report the same version as our current normalized
+# config and pass that to make as RUSTC
+
+# Create a temporary directory for the dummy rustc
+TMPDIR=$(mktemp -d)
+
+# Create the dummy rustc that always reports the same version
+cat > "$TMPDIR/rustc" << 'EOF'
+#!/bin/sh
+case "$1" in
+    --version|-vV)
+        echo "rustc 1.76.0"
+        echo "LLVM version: 17.0.6"
+        ;;
+    *)
+        ;;
+esac
+EOF
+chmod +x "$TMPDIR/rustc"
+
 for config in $CONFIG_LIST; do
     echo "Rebasing $config"
     if [[ $config == *"x86_64"* ]]; then
 	echo "Rebasing x86_64 config"
 	cp $config .config
-	make ARCH=x86_64  CROSS_COMPILE=scripts/dummy-tools/ olddefconfig
+	make ARCH=x86_64  CROSS_COMPILE=scripts/dummy-tools/ RUSTC=$TMPDIR/rustc olddefconfig
 	CONFIG_DIFF=$(diff --ignore-matching-lines='^# Linux/x86_64' .config $config | wc -l)
 	if [ $CONFIG_DIFF -eq 0 ]; then
 	    echo "No changes to x86_64 config"
@@ -81,7 +103,7 @@ for config in $CONFIG_LIST; do
     elif [[ $config == *"aarch64"* ]]; then
 	echo "Rebaseing aarch64 config"
 	cp $config .config
-	make ARCH=arm64 CROSS_COMPILE=scripts/dummy-tools/ olddefconfig
+	make ARCH=arm64 CROSS_COMPILE=scripts/dummy-tools/ RUSTC="$TMPDIR/rustc" olddefconfig
 	CONFIG_DIFF=$(diff --ignore-matching-lines='^# Linux/arm64' .config $config | wc -l)
 	if [ $CONFIG_DIFF -eq 0 ]; then
 	    echo "No changes to aarch64 config"
@@ -96,6 +118,8 @@ for config in $CONFIG_LIST; do
     fi
 done
 
+rm -rf $TMPDIR
+
 REPO_STATUS=$(git status -s)
 if [ ! -z "$REPO_STATUS" ]; then
     echo "Repository is not clean adding configs"