ci: Run xclippy aginst the custom target

Also, explain why we still need
  panic = "abort"
in the Cargo.toml

Signed-off-by: Joe Richey <joerichey@google.com>

Author: josephlr

.travis.yml

@@ -22,7 +22,7 @@ install:
 
 script:
   - cargo xbuild --release --target target.json
-  - cargo xclippy
+  - cargo xclippy --target target.json
   - cargo clippy --all-targets --all-features
   - cargo fmt --all -- --check
   - cargo test

Cargo.toml

@@ -4,14 +4,14 @@ version = "0.1.0"
 authors = ["Rob Bradford <robert.bradford@intel.com>"]
 edition = "2018"
 
-# the profile used for `cargo build`
+# Despite "panic-strategy": "abort" being set in target.json, panic = "abort" is
+# needed here to make "cargo check" and "cargo clippy" run without errors.
 [profile.dev]
-panic = "abort" # disable stack unwinding on panic
+panic = "abort"
 lto = true
 
-# the profile used for `cargo build --release`
 [profile.release]
-panic = "abort" # disable stack unwinding on panic
+panic = "abort"
 lto = true
 
 [dependencies]