tests: enable running `v test .` inside vlib/v/ too

cmd/tools/modules/testing/common.v

@@ -150,9 +150,9 @@ fn worker_trunner(mut p sync.PoolProcessor, idx int, thread_id int) voidptr {
 	}
 	tls_bench.no_cstep = true
 	dot_relative_file := p.get_string_item(idx)
-	mut relative_file := dot_relative_file
+	mut relative_file := dot_relative_file.replace('./', '')
 	if ts.root_relative {
-		relative_file = relative_file.replace(ts.vroot + os.path_separator, '').replace('./', '')
+		relative_file = relative_file.replace(ts.vroot + os.path_separator, '')
 	}
 	file := os.real_path(relative_file)
 	// Ensure that the generated binaries will be stored in the temporary folder.

vlib/v/tests/inout/compiler_test.v

@@ -7,6 +7,7 @@ fn test_all() {
 	mut total_errors := 0
 	vexe := os.getenv('VEXE')
 	vroot := os.dir(vexe)
+	os.chdir(vroot)
 	diff_cmd := util.find_working_diff_command() or {
 		''
 	}

vlib/v/tests/vmod_parser_test.v

@@ -1,6 +1,9 @@
 import vmod
 
+import os
+
 fn test_from_file() {
+	os.chdir(os.dir(os.getenv('VEXE')))
 	data := vmod.from_file('./v.mod') or {
 		panic(err)
 	}