Meta/run.py: Use if/elif instead of match

Less code, less indentation, and works with Py3.9.

(In return, the checked variable name is repeated in each conditional.)

Meta/run.py

@@ -292,14 +292,13 @@ def determine_qemu_kind() -> QEMUKind:
 
 
 def determine_serenity_arch() -> Arch:
-    match environ.get("SERENITY_ARCH"):
+    arch = environ.get("SERENITY_ARCH")
-        case "aarch64":
+    if arch == "aarch64":
         return Arch.Aarch64
-        case "riscv64":
+    if arch == "riscv64":
         return Arch.RISCV64
-        case "x86_64":
+    if arch == "x86_64":
         return Arch.x86_64
-        case _:
     raise RunError("Please specify a valid SerenityOS architecture")
 
 
@@ -327,12 +326,11 @@ def setup_qemu_binary(config: Configuration):
     if "SERENITY_QEMU_BIN" in environ:
         qemu_binary_basename = environ.get("SERENITY_QEMU_BIN")
     else:
-        match config.architecture:
+        if config.architecture == Arch.Aarch64:
-            case Arch.Aarch64:
             qemu_binary_basename = "qemu-system-aarch64"
-            case Arch.RISCV64:
+        elif config.architecture == Arch.RISCV64:
             qemu_binary_basename = "qemu-system-riscv64"
-            case Arch.x86_64:
+        elif config.architecture == Arch.x86_64:
             qemu_binary_basename = "qemu-system-x86_64"
     if qemu_binary_basename is None:
         raise RunError("QEMU binary could not be determined")
@@ -532,12 +530,11 @@ def setup_audio_backend(config: Configuration):
 
 def setup_audio_hardware(config: Configuration):
     provided_audio_hardware = environ.get("SERENITY_AUDIO_HARDWARE", "intelhda")
-    match provided_audio_hardware:
+    if provided_audio_hardware == "ac97":
-        case "ac97":
         config.audio_devices = ["ac97,audiodev=snd0"]
-        case "intelhda":
+    elif provided_audio_hardware == "intelhda":
         config.audio_devices = ["ich9-intel-hda", "hda-output,audiodev=snd0"]
-        case _:
+    else:
         raise RunError(f"Unknown audio hardware {provided_audio_hardware}. Supported values: ac97, intelhda")
 
     if config.machine_type.supports_pc_speaker() and config.architecture == Arch.x86_64:
@@ -690,12 +687,11 @@ hostfwd=tcp:{config.host_ip}:2222-10.0.2.15:22"
 
 
 def setup_kernel(config: Configuration):
-    match config.architecture:
+    if config.architecture == Arch.Aarch64:
-        case Arch.Aarch64:
         config.kernel_and_initrd_arguments = ["-kernel", "Kernel/Kernel"]
-        case Arch.RISCV64:
+    elif config.architecture == Arch.RISCV64:
         config.kernel_and_initrd_arguments = ["-kernel", "Kernel/Kernel.bin"]
-        case Arch.x86_64:
+    elif config.architecture == Arch.x86_64:
         config.kernel_and_initrd_arguments = ["-kernel", "Kernel/Prekernel/Prekernel", "-initrd", "Kernel/Kernel"]
 
 
@@ -733,8 +729,7 @@ def setup_machine_devices(config: Configuration):
         return
 
     # Machine specific base setups
-    match config.machine_type:
+    if config.machine_type in [MachineType.QEMU35Grub, MachineType.QEMU35]:
-        case MachineType.QEMU35Grub | MachineType.QEMU35:
         config.qemu_machine = "q35"
         config.vga_type = None
         # We set up our own custom display devices.
@@ -768,7 +763,7 @@ def setup_machine_devices(config: Configuration):
         )
         config.character_devices.append("stdio,id=stdout,mux=on")
         config.enable_usb = True
-        case MachineType.MicroVM | MachineType.ISAPC:
+    elif config.machine_type in [MachineType.MicroVM, MachineType.ISAPC]:
         config.character_devices.append("stdio,id=stdout,mux=on")
         config.qemu_cpu = "qemu64"
         config.cpu_count = None
@@ -783,7 +778,7 @@ def setup_machine_devices(config: Configuration):
         else:  # ISAPC
             config.qemu_machine = "isapc"
 
-        case MachineType.CI:
+    elif config.machine_type == MachineType.CI:
         config.display_backend = "none"
         config.audio_backend = None
         config.audio_devices = []
@@ -795,7 +790,7 @@ def setup_machine_devices(config: Configuration):
             config.add_device("ich9-ahci")
             config.extra_arguments.extend(["-debugcon", "file:debug.log"])
 
-        case _:
+    else:
         # Default machine
         config.network_default_device = f"{config.network_default_device},bus=bridge1"
         config.add_devices(
@@ -817,15 +812,14 @@ def setup_machine_devices(config: Configuration):
 
     # Modifications for machine types that are *mostly* like the default,
     # but not entirely (especially in terms of networking).
-    match config.machine_type:
+    if config.machine_type in [MachineType.QEMUWithoutNetwork, MachineType.QEMU35Grub]:
-        case MachineType.QEMUWithoutNetwork | MachineType.QEMU35Grub:
         config.network_backend = None
         config.network_default_device = config.ethernet_device_type
         config.packet_logging_arguments = []
-        case MachineType.QEMUTap:
+    elif config.machine_type == MachineType.QEMUTap:
         config.network_backend = "tap,ifname=tap0,id=br0"
         config.network_default_device = f"{config.ethernet_device_type},netdev=br0"
-        case MachineType.QEMUGrub | MachineType.QEMUExtLinux:
+    elif config.machine_type in [MachineType.QEMUGrub, MachineType.QEMUExtLinux]:
         config.kernel_cmdline = []