Increase disk size to 160GB

This commit increases the image disk size to 160GB because the previous
size of 100GB was insufficient for building the GNU toolchains with many
multi-libs (e.g. arm and riscv64).

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

sdk-build-macos.pkr.hcl

@@ -12,7 +12,7 @@ source "tart-cli" "tart" {
   vm_name      = "sdk-build-macos"
   cpu_count    = 4
   memory_gb    = 8
-  disk_size_gb = 100
+  disk_size_gb = 160
   headless     = true
   ssh_password = "admin"
   ssh_username = "admin"