Fixes #802, #803 and #3775 - genscript issues (#7677)

* Fixes #802, #803 and #3775 - genscript issues

* Test case for genscript

* Test script

* Verify on Linux

* Update categories.nim

* Fix merge

* Improve test framework

* Windows fixes

compiler/commands.nim

@@ -652,6 +652,7 @@ proc processSwitch(switch, arg: string, pass: TCmdLinePass, info: TLineInfo;
   of "genscript", "gendeps":
     expectNoArg(switch, arg, pass, info)
     incl(gGlobalOptions, optGenScript)
+    incl(gGlobalOptions, optCompileOnly)
   of "colors": processOnOffSwitchG({optUseColors}, arg, pass, info)
   of "lib":
     expectArg(switch, arg, pass, info)

compiler/extccomp.nim

@@ -470,8 +470,9 @@ proc execExternalProgram*(cmd: string, msg = hintExecuting) =
 
 proc generateScript(projectFile: string, script: Rope) =
   let (dir, name, ext) = splitFile(projectFile)
-  writeRope(script, dir / addFileExt("compile_" & name,
+  writeRope(script, getNimcacheDir() / addFileExt("compile_" & name,
                                      platform.OS[targetOS].scriptExt))
+  copyFile(libpath / "nimbase.h", getNimcacheDir() / "nimbase.h")
 
 proc getOptSpeed(c: TSystemCC): string =
   result = getConfigVar(c, ".options.speed")