GNUmakefile: add spellfix target, use it. (#4387)

TODO: Remove the go.mod/go.sum in internal/tools once doing so doesn't break CI (e.g. once we drop support for go 1.19)

* builder/cc1as.h: fix typo found by 'make spell'
* GNUmakefile: remove exception for inbetween, fix instance now found by 'make spell'
* GNUmakefile: remove exception for programmmer, fix instance now found by 'make spell'
* go.mod: use updated misspell. GNUmakefile: add spellfix target, use it.
* ignore directories properly when invoking spellchecker.
* make spell: give internal/tools its own go.mod, as misspell requires newer go
* make lint: depend on tools and run the installed revive
(which was perhaps implied by the change that added revive to internal/tools,
but not required in GNUmakefile until we gave internal/tools its own temporary go.mod)
* .github: now that 'make spell' works well, run it from CI
* GNUmakefile: make spell now aborts if it finds misspelt words, so what it finds doesn't get lost in CI logs
* GNUmakefile: tools: avoid -C option on go generate to make test-llvm15-go119 circleci job happy, see
https://cs.opensource.google/go/go/+/2af48cbb7d85e5fdc635e75b99f949010c607786
* internal/tools/go.mod: fix format of go version to leave out patchlevel, else go complains.

diagnostics/diagnostics.go

@@ -43,7 +43,7 @@ func CreateDiagnostics(err error) ProgramDiagnostic {
 	if err == nil {
 		return nil
 	}
-	// Right now, the compiler will only show errors for the first pacakge that
+	// Right now, the compiler will only show errors for the first package that
 	// fails to build. This is likely to change in the future.
 	return ProgramDiagnostic{
 		createPackageDiagnostic(err),
@@ -147,7 +147,7 @@ func createDiagnostics(err error) []Diagnostic {
 					// last package
 					fmt.Fprintln(buf, "\timports", pkgPath+": "+err.Err.Error())
 				} else {
-					// not the last pacakge
+					// not the last package
 					fmt.Fprintln(buf, "\timports", pkgPath)
 				}
 			}