feat(selfhost): achieve binary-identical selfhost loop

- Add -Wl,--build-id=none to C compilation flags (removes non-deterministic build ID)
- Update Makefile selfhost-loop to strip debug info before ELF comparison
- Bootstrap compiler and selfhost compiler both deterministic

Makefile

@@ -123,14 +123,16 @@ selfhost-loop: build
 	else \
 		echo "  C output: DIFFERENT ✗"; \
 	fi
-	@echo "Comparing ELF binaries..."
-	@if diff build/selfhost-loop-a/build/buxc2 build/selfhost-loop-b/build/buxc2 > /dev/null 2>&1; then \
+	@echo "Comparing ELF binaries (stripped)..."
+	@cp build/selfhost-loop-a/build/buxc2 /tmp/buxc2_a && strip -d /tmp/buxc2_a
+	@cp build/selfhost-loop-b/build/buxc2 /tmp/buxc2_b && strip -d /tmp/buxc2_b
+	@if diff /tmp/buxc2_a /tmp/buxc2_b > /dev/null 2>&1; then \
 		echo "  ELF binary: IDENTICAL ✓"; \
 		echo "=== Selfhost loop PASSED ==="; \
 	else \
-		echo "  ELF binary: DIFFERENT ✗ (may be due to timestamps)"; \
-		echo "  C output was identical — ELF difference is likely linker non-determinism"; \
-		echo "=== Selfhost loop: C codegen deterministic ✓, ELF non-deterministic (expected) ==="; \
+		echo "  ELF binary: DIFFERENT ✗"; \
+		echo "=== Selfhost loop FAILED ==="; \
+		exit 1; \
 	fi
 
 lsp: tools/bux-lsp

bootstrap/cli.nim

@@ -488,7 +488,7 @@ proc cmdBuild*(args: seq[string], opts: GlobalOptions): int =
   # Compile with cc
   let outputName = if pctx.man.name != "": pctx.man.name else: "bux_out"
   let outputFile = buildDir / outputName
-  let ccCmd = &"cc -O0 -g -pthread -o {outputFile} {cFile} {runtimeDst} {ioDst} -lm -lcrypto 2>&1"
+  let ccCmd = &"cc -O0 -g -pthread -Wl,--build-id=none -o {outputFile} {cFile} {runtimeDst} {ioDst} -lm -lcrypto 2>&1"
   if opts.verbose:
     printInfo(&"running: {ccCmd}", useColor)
   let (output, exitCode) = execCmdEx(ccCmd)

src/cli.bux

@@ -255,13 +255,13 @@ func Cli_Build(srcPath: String, outPath: String, targetTriple: String, isRelease
     if !String_Eq(targetTriple, "") {
         StringBuilder_Append(&cmdBuf, "clang ");
         StringBuilder_Append(&cmdBuf, optFlags);
-        StringBuilder_Append(&cmdBuf, " -pthread -target ");
+        StringBuilder_Append(&cmdBuf, " -pthread -Wl,--build-id=none -target ");
         StringBuilder_Append(&cmdBuf, targetTriple);
         StringBuilder_Append(&cmdBuf, " ");
     } else {
         StringBuilder_Append(&cmdBuf, "cc ");
         StringBuilder_Append(&cmdBuf, optFlags);
-        StringBuilder_Append(&cmdBuf, " -pthread ");
+        StringBuilder_Append(&cmdBuf, " -pthread -Wl,--build-id=none ");
     }
     StringBuilder_Append(&cmdBuf, "-o ");
     StringBuilder_Append(&cmdBuf, outPath);
@@ -1181,13 +1181,13 @@ func Cli_BuildProject(projectDir: String, targetTriple: String, isRelease: bool)
     if !String_Eq(targetTriple, "") {
         StringBuilder_Append(&ccBuf, "clang ");
         StringBuilder_Append(&ccBuf, optFlags2);
-        StringBuilder_Append(&ccBuf, " -pthread -target ");
+        StringBuilder_Append(&ccBuf, " -pthread -Wl,--build-id=none -target ");
         StringBuilder_Append(&ccBuf, targetTriple);
         StringBuilder_Append(&ccBuf, " ");
     } else {
         StringBuilder_Append(&ccBuf, "cc ");
         StringBuilder_Append(&ccBuf, optFlags2);
-        StringBuilder_Append(&ccBuf, " -pthread ");
+        StringBuilder_Append(&ccBuf, " -pthread -Wl,--build-id=none ");
     }
     StringBuilder_Append(&ccBuf, "-o ");
     StringBuilder_Append(&ccBuf, outBin);