[engine] Use result of slices.Compact

slices.Compact returns a value instead of mutating the input, so the old
code was not actually removing duplicates.

This only mattered when files were based as positional arguments to
`shac check`, which is not super common, and even less common that
someone would list the same file twice, hence why we didn't notice it
until it started being raised by the "lint" GitHub workflow.

I also updated the `govet` shac check to include the analyzer that was
catching this in the GitHub workflow.

Change-Id: I4a0eb6014d9d9dc1edc225ea60bf76d1fcc3f950

Author: orn688

checks/go.star

@@ -269,6 +269,7 @@ def govet(
         # analyzers that aren't enforced by the other linters.
         analyzers = [
             "copylocks",
+            "unusedresult",
         ]):
     """Enforces `go vet`.
 

internal/engine/run.go

@@ -612,7 +612,7 @@ func normalizeFiles(files []string, root string) ([]file, error) {
 	}
 
 	slices.Sort(relativized)
-	slices.Compact(relativized)
+	relativized = slices.Compact(relativized)
 
 	var res []file
 	for _, f := range relativized {

internal/engine/version.go

@@ -26,7 +26,7 @@ var (
 	// Version is the current tool version.
 	//
 	// TODO(maruel): Add proper version, preferably from git tag.
-	Version = shacVersion{0, 1, 20}
+	Version = shacVersion{0, 1, 21}
 )
 
 func (v shacVersion) String() string {