QEMU Apple Silicon: Find BIOS FD wherever

QEmu normally install BIOS images under `/usr/local` prefix, but
Homebrew installs them under `/opt/homebrew`.  This change searches both
locations and then puts back to an unpathed name if it doesn't find the
BIOS.  (I imitated other architectures' implemenations in that failback
behavior.)

[NO TESTS NEEDED]

Signed-off-by: Jonathan Springer <[email protected]>

pkg/machine/qemu/options_darwin_arm64.go

@@ -1,6 +1,7 @@
 package qemu
 
 import (
+	"os"
 	"os/exec"
 	"path/filepath"
 )
@@ -15,7 +16,7 @@ func (v *MachineVM) addArchOptions() []string {
 		"-accel", "hvf",
 		"-cpu", "cortex-a57",
 		"-M", "virt,highmem=off",
-		"-drive", "file=/usr/local/share/qemu/edk2-aarch64-code.fd,if=pflash,format=raw,readonly=on",
+		"-drive", "file=" + getEdk2CodeFd("edk2-aarch64-code.fd") + ",if=pflash,format=raw,readonly=on",
 		"-drive", "file=" + ovmfDir + ",if=pflash,format=raw"}
 	return opts
 }
@@ -34,3 +35,23 @@ func (v *MachineVM) archRemovalFiles() []string {
 func getOvmfDir(imagePath, vmName string) string {
 	return filepath.Join(filepath.Dir(imagePath), vmName+"_ovmf_vars.fd")
 }
+
+/*
+ *  QEmu can be installed in multiple locations on MacOS, especially on
+ *  Apple Silicon systems.  A build from source will likely install it in
+ *  /usr/local/bin, whereas Homebrew package management standard is to
+ *  install in /opt/homebrew
+ */
+func getEdk2CodeFd(name string) string {
+	dirs := []string{
+		"/usr/local/share/qemu",
+		"/opt/homebrew/share/qemu",
+	}
+	for _, dir := range dirs {
+		fullpath := filepath.Join(dir, name)
+		if _, err := os.Stat(fullpath); err == nil {
+			return fullpath
+		}
+	}
+	return name
+}