add /opt/homebrew check for arm64 Macs

build.sh

@@ -1,4 +1,9 @@
 #!/bin/sh
+if [[ -z "$LIBRARY_PATH" && -d /opt/homebrew ]]; then
+	echo "Using /opt/homebrew for LIBRARY_PATH and CPATH"
+	export LIBRARY_PATH=/opt/homebrew/lib
+	export CPATH=/opt/homebrew/include
+fi
 export MAUTRIX_VERSION=$(cat go.mod | grep 'maunium.net/go/mautrix ' | awk '{ print $2 }')
 export GO_LDFLAGS="-s -w -X main.Tag=$(git describe --exact-match --tags 2>/dev/null) -X main.Commit=$(git rev-parse HEAD) -X 'main.BuildTime=`date '+%b %_d %Y, %H:%M:%S'`' -X 'maunium.net/go/mautrix.GoModVersion=$MAUTRIX_VERSION'"
 go build -ldflags "$GO_LDFLAGS" -o mautrix-meta "$@"