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.

compileopts/config.go

@@ -60,7 +60,7 @@ func (c *Config) GOOS() string {
 }
 
 // GOARCH returns the GOARCH of the target. This might not always be the actual
-// archtecture: for example, the AVR target is not supported by the Go standard
+// architecture: for example, the AVR target is not supported by the Go standard
 // library so such targets will usually pretend to be linux/arm.
 func (c *Config) GOARCH() string {
 	return c.Target.GOARCH
@@ -461,7 +461,7 @@ func (c *Config) BinaryFormat(ext string) string {
 
 // Programmer returns the flash method and OpenOCD interface name given a
 // particular configuration. It may either be all configured in the target JSON
-// file or be modified using the -programmmer command-line option.
+// file or be modified using the -programmer command-line option.
 func (c *Config) Programmer() (method, openocdInterface string) {
 	switch c.Options.Programmer {
 	case "":