fix arm/arm64 builds by enabling CGO

Enable CGO for all arm/arm64 builds to address Go bug.

golang/go#32912

Also restrict arm(64) builds to Linux only as it is the only one anyone
is using.

Makefile

@@ -28,7 +28,8 @@ GOARCH ?= $(shell go env GOARCH)
 # Default os-arch combination to build
 XC_OS ?= darwin freebsd linux netbsd openbsd solaris windows
 XC_ARCH ?= 386 amd64 arm arm64
-XC_EXCLUDE ?= darwin/arm solaris/386 solaris/arm windows/arm darwin/arm64 freebsd/arm64 netbsd/arm64 openbsd/arm64 solaris/arm64 windows/arm64
+# XC_EXCLUDE "arm64" entries excludes both arm and arm64
+XC_EXCLUDE ?= darwin/arm64 freebsd/arm64 netbsd/arm64 openbsd/arm64 solaris/386 solaris/arm64 windows/arm64
 
 # GPG Signing key (blank by default, means no GPG signing)
 GPG_KEY ?=
@@ -52,8 +53,15 @@ define make-xc-target
 		@printf "%s%20s %s\n" "-->" "${1}/${2}:" "${PROJECT} (excluded)"
   else
 		@printf "%s%20s %s\n" "-->" "${1}/${2}:" "${PROJECT}"
+		case "$2" in \
+			arm) export CGO_ENABLED="1" ; \
+				  export GOARM=5 \
+				  export CC="arm-linux-gnueabi-gcc" ;; \
+			arm64) export CGO_ENABLED="1" ; \
+				  export CC="aarch64-linux-gnu-gcc" ;; \
+			*) export CGO_ENABLED="0" ;; \
+		esac ; \
 		env \
-			CGO_ENABLED="0" \
 			GOOS="${1}" \
 			GOARCH="${2}" \
 			go build \