Refactor firmware flasher into submodule

This is a lot cleaner than cd-ing above the repository (potentially
dangerous in CI because the state of the directory above the repository
is not guaranteed) and doing a 'git clone'. This will also allow
the submodule's commit to be pinned and not change without developer
intent.

.gitlab-ci.yml

@@ -34,15 +34,13 @@ build-flasher:
   stage: build-flasher
   script:
     - mkdir flasher
-    - cd ..
-    - git clone https://gitlab.scd31.com/cats/firmware-flasher
-    - cd firmware-flasher
-    - cp ../mobile-transceiver-software/firmware.bin firmware.bin
+    - cd firmware-flasher # cd into submodule
+    - cp ../firmware.bin firmware.bin
     - cargo build --release --target arm-unknown-linux-gnueabihf
     - cargo build --release --target x86_64-pc-windows-gnu
-    - cp target/arm-unknown-linux-gnueabihf/release/stm32-firmware-flasher ../mobile-transceiver-software/flasher/flasher-linux
-    - arm-linux-gnueabihf-strip ../mobile-transceiver-software/flasher/flasher-linux
-    - cp target/x86_64-pc-windows-gnu/release/stm32-firmware-flasher.exe ../mobile-transceiver-software/flasher/flasher-windows.exe
+    - cp target/arm-unknown-linux-gnueabihf/release/stm32-firmware-flasher ../flasher/flasher-linux
+    - arm-linux-gnueabihf-strip ../flasher/flasher-linux
+    - cp target/x86_64-pc-windows-gnu/release/stm32-firmware-flasher.exe ../flasher/flasher-windows.exe
   artifacts:
     paths:
       - flasher/*

.gitmodules

+[submodule "firmware-flasher"]
+	path = firmware-flasher
+	url = https://gitlab.scd31.com/cats/firmware-flasher

firmware-flasher @ 87fb2352

+Subproject commit 87fb2352473381232e46592a75f6876a816cc171