Build nightly rustfmt using --all-features in CI

Previously we were only building rustfmt with default features in CI. We
recently received a report that rustfmt was unable to compile with the
`generic-simd` feature, which is not enabled by default. To prevent a
similar situation in the future we'll start build nightly rustfmt with
all features enabled.

ci/build_and_test.bat

@@ -6,7 +6,11 @@ rustc -Vv || exit /b 1
 cargo -V || exit /b 1
 
 :: Build and test main crate
-cargo build --locked || exit /b 1
+if "%CFG_RELEASE_CHANNEL%"=="nightly" (
+    cargo build --locked --all-features || exit /b 1
+) else (
+    cargo build --locked || exit /b 1
+)
 cargo test || exit /b 1
 
 :: Build and test other crates

ci/build_and_test.sh

@@ -10,7 +10,11 @@ rustc -Vv
 cargo -V
 
 # Build and test main crate
-cargo build --locked
+if [ "$CFG_RELEASE_CHANNEL" == "nightly" ]; then
+    cargo build --locked --all-features
+else
+    cargo build --locked
+fi
 cargo test
 
 # Build and test other crates