fix(ci): add llvm-symbolizer symlink for Alpine Linux

Alpine's `llvm21` package installs the symbolizer as `llvm21-symbolizer`
(version-prefixed) rather than `llvm-symbolizer`. The `bun-tracestrings`
CI crash report parser uses `Bun.which("llvm-symbolizer")` and fails to
find the binary on Alpine ARM64 (and x64).

- bootstrap.sh: after installing LLVM on Alpine, create an unversioned
  `/usr/bin/llvm-symbolizer` symlink if one doesn't already exist
- crash_handler.zig: add `llvm21-symbolizer` (Alpine naming) to the
  fallback list so crash symbolization works even without the symlink

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

scripts/bootstrap.sh

@@ -1130,7 +1130,18 @@ install_llvm() {
 			"clang$(llvm_version)" \
 			"scudo-malloc" \
 			"lld$(llvm_version)" \
-			"llvm$(llvm_version)-dev" # Ensures llvm-symbolizer is installed
+			"llvm$(llvm_version)-dev"
+		# Alpine uses versioned binary names (e.g. llvm-symbolizer-21, llvm21-symbolizer).
+		# Create unversioned symlinks so tools like bun-tracestrings can find them.
+		if ! command -v llvm-symbolizer > /dev/null 2>&1; then
+			local llvm_v="$(llvm_version)"
+			# Try Debian-style naming (llvm-symbolizer-21), then Alpine-style (llvm21-symbolizer)
+			if command -v "llvm-symbolizer-${llvm_v}" > /dev/null 2>&1; then
+				execute_sudo ln -sf "$(which "llvm-symbolizer-${llvm_v}")" /usr/bin/llvm-symbolizer
+			elif command -v "llvm${llvm_v}-symbolizer" > /dev/null 2>&1; then
+				execute_sudo ln -sf "$(which "llvm${llvm_v}-symbolizer")" /usr/bin/llvm-symbolizer
+			fi
+		fi
 		;;
 	esac
 }

src/crash_handler.zig

@@ -1700,8 +1700,9 @@ pub fn dumpStackTrace(trace: std.builtin.StackTrace, limits: WriteStackTraceLimi
 
     const programs: []const [:0]const u8 = switch (bun.Environment.os) {
         .windows => &.{"pdb-addr2line"},
-        // if `llvm-symbolizer` doesn't work, also try `llvm-symbolizer-21`
-        else => &.{ "llvm-symbolizer", "llvm-symbolizer-21" },
+        // if `llvm-symbolizer` doesn't work, also try versioned names:
+        // `llvm-symbolizer-21` (Debian/Ubuntu) or `llvm21-symbolizer` (Alpine)
+        else => &.{ "llvm-symbolizer", "llvm-symbolizer-21", "llvm21-symbolizer" },
     };
     for (programs) |program| {
         var arena = bun.ArenaAllocator.init(bun.default_allocator);