Reduce disk usage in CI

Recently github appears to have reduced the available free disk
space in actions runs, causing CI to fail with out of space errors.
Here we simply run `cargo clean` a few times in CI to reduce our
disk usage somewhat.

Author: TheBlueMatt

.github/workflows/build.yml

@@ -51,7 +51,7 @@ jobs:
           shellcheck ci/ci-tests.sh
       - name: Run CI script
         shell: bash # Default on Winblows is powershell
-        run: ./ci/ci-tests.sh
+        run: CI_MINIMIZE_DISK_USAGE=1 ./ci/ci-tests.sh
 
   coverage:
     strategy:

ci/ci-tests.sh

@@ -80,6 +80,7 @@ if [ "$RUSTC_MINOR_VERSION" -gt 55 ]; then
 	echo -e "\n\nTest Custom Message Macros"
 	pushd lightning-custom-message
 	cargo test --verbose --color always
+	[ "$CI_MINIMIZE_DISK_USAGE" != "" ] && cargo clean
 	popd
 fi
 
@@ -130,17 +131,20 @@ else
 	[ "$RUSTC_MINOR_VERSION" -lt 60 ] && cargo update -p memchr --precise "2.5.0" --verbose
 	cargo check --verbose --color always
 fi
+[ "$CI_MINIMIZE_DISK_USAGE" != "" ] && cargo clean
 popd
 
 # Test that we can build downstream code with only the "release pins".
 pushd msrv-no-dev-deps-check
 PIN_RELEASE_DEPS
 cargo check
+[ "$CI_MINIMIZE_DISK_USAGE" != "" ] && cargo clean
 popd
 
 if [ -f "$(which arm-none-eabi-gcc)" ]; then
 	pushd no-std-check
 	cargo build --target=thumbv7m-none-eabi
+	[ "$CI_MINIMIZE_DISK_USAGE" != "" ] && cargo clean
 	popd
 fi