Fix Walter's bash faux pas.

lubuntu/modules/before_bootloader_context.conf

@@ -10,7 +10,7 @@ firmwareType:
              timeout: 10
         -    command: apt-get update
              timeout: 120
-        -    command: apt install -y --no-upgrade -o Acquire::gpgv::Options::=--ignore-time-conflict grub-efi-$(if [ "$(grep 64 /sys/firmware/efi/fw_platform_size)" ]; then echo amd64-signed; else echo ia32; fi)
+        -    command: apt install -y --no-upgrade -o Acquire::gpgv::Options::=--ignore-time-conflict grub-efi-$(if grep -q 64 /sys/firmware/efi/fw_platform_size; then echo amd64-signed; else echo ia32; fi)
              timeout: 300
         -    command: apt install -y --no-upgrade -o Acquire::gpgv::Options::=--ignore-time-conflict shim-signed
              timeout: 300