os: use _wputenv instead of _putenv to stay in sync with _wgetenv (fix changing env variables with non ASCII content on windows) (#22920)

vlib/builtin/cfns.c.v

@@ -327,6 +327,7 @@ fn C._wsystem(command &u16) int
 fn C._wgetenv(varname &u16) voidptr
 
 fn C._putenv(envstring &char) int
+fn C._wputenv(envstring &u16) int
 
 fn C._waccess(path &u16, mode int) int
 

vlib/os/environment.c.v

@@ -45,15 +45,18 @@ pub fn getenv_opt(key string) ?string {
 // os.setenv sets the value of an environment variable with `name` to `value`.
 pub fn setenv(name string, value string, overwrite bool) int {
 	$if windows {
-		format := '${name}=${value}'
+		format := '${name}=${value}'.to_wide()
+		defer {
+			unsafe { free(voidptr(format)) }
+		}
 		if overwrite {
 			unsafe {
-				return C._putenv(&char(format.str))
+				return C._wputenv(format)
 			}
 		} else {
 			if getenv(name).len == 0 {
 				unsafe {
-					return C._putenv(&char(format.str))
+					return C._wputenv(format)
 				}
 			}
 		}
@@ -68,8 +71,11 @@ pub fn setenv(name string, value string, overwrite bool) int {
 // os.unsetenv clears an environment variable with `name`.
 pub fn unsetenv(name string) int {
 	$if windows {
-		format := '${name}='
-		return C._putenv(&char(format.str))
+		format := '${name}='.to_wide()
+		defer {
+			unsafe { free(voidptr(format)) }
+		}
+		return C._wputenv(format)
 	} $else {
 		return C.unsetenv(&char(name.str))
 	}

vlib/os/environment_test.v

@@ -52,3 +52,19 @@ fn test_getenv_empty_var() {
 	os.setenv('empty${key}', '""', false)
 	assert os.getenv('empty${key}') == '""'
 }
+
+fn test_environ_non_ascii() {
+	os.setenv('Büro', 'gebäude', false)
+	assert os.getenv('Büro') == 'gebäude'
+	os.setenv('Büro', 'gebäudehaus', true)
+	assert os.getenv('Büro') == 'gebäudehaus'
+	os.setenv('Büro', 'gebäudehaus in der Straße', true)
+	assert os.getenv('Büro') == 'gebäudehaus in der Straße'
+	os.unsetenv('Büro')
+	assert os.getenv('Büro') == ''
+
+	os.setenv('한국어', '초보자를 위한', false)
+	assert os.getenv('한국어') == '초보자를 위한'
+	os.unsetenv('한국어')
+	assert os.getenv('한국어') == ''
+}