fix: enable Mac builds using Homebrew LLVM

Apple's Clang doesn't support the wasm32-unknown-unknown target,
causing secp256k1-sys compilation to fail on Mac. This change
automatically detects Mac and uses Homebrew's LLVM which has
proper WASM support.

Changes:
- Makefile: Auto-detect Mac and set CC/AR to use Homebrew LLVM
- Makefile: Remove trailing slashes from target declarations for
  compatibility with both old (Mac 3.81) and new (Linux 4.x) Make
- package.json: Fix Make target names to match Makefile
- scripts/wasm-pack-test.sh: Wrapper script to set correct compiler
  for wasm-pack tests on Mac
- README.md: Update build instructions for Mac

This allows Mac users to build with 'npm run build' without Docker,
while maintaining full compatibility with Linux CI builds.

Tested on Mac (Apple Silicon)
Requires: brew install llvm"

Ticket: BTC-0

Author: lcovar

packages/wasm-utxo/Makefile

@@ -6,6 +6,24 @@ ifdef WASM_PACK_DEV
 	WASM_PACK_FLAGS += --dev
 endif
 
+# Auto-detect Mac and use Homebrew LLVM for WASM compilation
+# Apple's Clang doesn't support wasm32-unknown-unknown target
+UNAME_S := $(shell uname -s)
+
+ifeq ($(UNAME_S),Darwin)
+  # Mac detected - check for Homebrew LLVM installation
+  HOMEBREW_LLVM := $(shell brew --prefix llvm 2>/dev/null)
+  
+  ifdef HOMEBREW_LLVM
+    export CC = $(HOMEBREW_LLVM)/bin/clang
+    export AR = $(HOMEBREW_LLVM)/bin/llvm-ar
+    $(info Using Homebrew LLVM: $(HOMEBREW_LLVM))
+  else
+    $(warning Homebrew LLVM not found. Install with: brew install llvm)
+    $(warning Continuing with system clang - may fail on Apple Silicon)
+  endif
+endif
+
 define WASM_PACK_COMMAND
 	$(WASM_PACK) build --no-opt --out-dir $(1) $(WASM_PACK_FLAGS) --target $(2)
 endef
@@ -34,16 +52,16 @@ define BUILD
 	$(call SHOW_WASM_SIZE,$(1))
 endef
 
-.PHONY: js/wasm/
-js/wasm/:
+.PHONY: js/wasm
+js/wasm:
 	$(call BUILD,$@,bundler)
 
-.PHONY: dist/esm/js/wasm/
-dist/esm/js/wasm/:
+.PHONY: dist/esm/js/wasm
+dist/esm/js/wasm:
 	$(call BUILD,$@,bundler)
 
-.PHONY: dist/cjs/js/wasm/
-dist/cjs/js/wasm/:
+.PHONY: dist/cjs/js/wasm
+dist/cjs/js/wasm:
 	$(call BUILD,$@,nodejs)
 
 .PHONY: lint

packages/wasm-utxo/README.md

@@ -24,10 +24,20 @@ This project is under active development.
 
 ## Building
 
-If your system has problems with `wasm-pack` (Mac M1), you can use the `Container.mk` Makefile to build the wasm files:
+### Mac
+
+Requires Homebrew LLVM (Apple's Clang doesn't support WASM targets):
+
+```bash
+brew install llvm
+npm run build
+```
+
+### Docker (optional)
+
+If you prefer a containerized build environment:
 
 ```bash
-cd packages/wasm-utxo
 make -f Container.mk build-image
 make -f Container.mk build-wasm
 ```

packages/wasm-utxo/package.json

@@ -36,12 +36,12 @@
     "test": "npm run test:mocha && npm run test:wasm-pack && npm run test:imports",
     "test:mocha": "mocha --recursive test",
     "test:wasm-pack": "npm run test:wasm-pack-node && npm run test:wasm-pack-chrome",
-    "test:wasm-pack-node": "wasm-pack test --node",
-    "test:wasm-pack-chrome": "wasm-pack test --headless --chrome",
+    "test:wasm-pack-node": "./scripts/wasm-pack-test.sh --node",
+    "test:wasm-pack-chrome": "./scripts/wasm-pack-test.sh --headless --chrome",
     "test:esm-import": "node --experimental-wasm-modules bundler-test/test-esm-import.mjs",
     "test:cjs-import": "node bundler-test/test-cjs-import.cjs",
     "test:imports": "npm run test:esm-import && npm run test:cjs-import",
-    "build:wasm": "make js/wasm/ && make dist/esm/js/wasm/ && make dist/cjs/js/wasm/",
+    "build:wasm": "make js/wasm && make dist/esm/js/wasm && make dist/cjs/js/wasm",
     "build:ts-esm": "tsc",
     "build:ts-cjs": "tsc --project tsconfig.cjs.json",
     "build:ts": "npm run build:ts-esm && npm run build:ts-cjs",

packages/wasm-utxo/scripts/wasm-pack-test.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+# Wrapper script for wasm-pack test that sets correct compiler on Mac
+
+# Detect Mac and set LLVM compiler
+if [[ "$(uname -s)" == "Darwin" ]]; then
+    LLVM_PATH=$(brew --prefix llvm 2>/dev/null)
+    if [ -n "$LLVM_PATH" ]; then
+        export CC="$LLVM_PATH/bin/clang"
+        export AR="$LLVM_PATH/bin/llvm-ar"
+    fi
+fi
+
+# Run wasm-pack test with all passed arguments
+wasm-pack test "$@"
+