internal/rosa/cmake: pass correct prefix

This can change build output similar to autotools --prefix and DESTDIR, but was not clearly indicated to do so.

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

internal/rosa/cmake.go

@@ -198,9 +198,9 @@ cmake -G ` + generate + ` \
 			}
 		}
 	}), " \\\n\t") + ` \
-	-DCMAKE_INSTALL_PREFIX=/work/system \
+	-DCMAKE_INSTALL_PREFIX=/system \
 	'/usr/src/` + name + `/` + path.Join(attr.Append...) + `'
 cmake --build .` + jobs + `
-cmake --install .
+cmake --install . --prefix=/work/system
 ` + attr.Script
 }