internal/rosa: remove unused helpers

These are no longer needed after migration.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/cmake.go

@@ -11,7 +11,7 @@ var (
 	_ninja = H("ninja")
 )
 
-// CMakeHelper is the [CMake] build system helper.
+// CMakeHelper builds and tests a CMake project with specified CACHE entries.
 type CMakeHelper struct {
 	// Path elements joined with source.
 	Append []string
@@ -34,7 +34,7 @@ type CMakeHelper struct {
 
 var _ Helper = new(CMakeHelper)
 
-// extra returns a hardcoded slice of [CMake] and [Ninja].
+// extra returns the cmake handle alongside either ninja or make.
 func (attr *CMakeHelper) extra(int) P {
 	if attr != nil && attr.Make {
 		return P{_cmake, _make}