remove unknown test, add glibc test

vlib/v/gen/c/testdata/comp_if_unknown.vv

@@ -1,9 +0,0 @@
-fn main() {
-	mut x := 1
-	$if glibc {
-		x = 2
-	} $else {
-		x = 3
-	}
-	println('done')
-}

vlib/v/tests/comptime/comptime_if_glibc_test.v

@@ -0,0 +1,21 @@
+fn test_comptime_if_glibc() {
+	mut x := 1
+	mut result := ''
+	$if glibc {
+		result += ' glibc'
+		x = 2
+	} $else {
+		result += ' else glibc'
+		x = 3
+	}
+
+	$if !glibc {
+		result += ' !glibc'
+	} $else {
+		result += ' else !glibc'
+	}
+
+	println(result)
+	assert result == ' glibc else !glibc' || result == ' else glibc  !glibc'
+	println('done')
+}