runtime: simplify nr_cpus(), add a test for nr_jobs()

vlib/runtime/runtime.v

@@ -14,13 +14,6 @@ fn C.sysconf(name int) i64
 fn C.GetCurrentProcessorNumber() u32
 //}
 
-pub fn nr_cpus() int {
-	$if windows {
-		return nr_cpus_win()
-	}
-	return nr_cpus_nix()
-}
-
 pub fn nr_jobs() int {
 	mut cpus := nr_cpus()
 	// allow for overrides, for example using `VJOBS=32 ./v test .`
@@ -32,25 +25,21 @@ pub fn nr_jobs() int {
 }
 
 pub fn is_32bit() bool {
-	mut x := false
-	$if x32 { x = true }
-	return x
+	$if x32 { return true }
+	return false
 }
 
 pub fn is_64bit() bool {
-	mut x := false
-	$if x64 { x = true }
-	return x
+	$if x64 { return true }
+	return false
 }
 
 pub fn is_little_endian() bool {
-	mut x := false
-	$if little_endian { x = true }
-	return x
+	$if little_endian { return true }
+	return false
 }
 
 pub fn is_big_endian() bool {
-	mut x := false
-	$if big_endian { x = true }
-	return x
+	$if big_endian { return true }
+	return false
 }