win32/rmdir_r.cpp: Check directory exists beforehand

rmdir_r's POSIX counterpart returns 0 on non-existing directories.
However, when SHFileOperation is called on a non-existing directory,
usually with DE_INVALIDFILES (0x7C) as its return code, although it is
considered unreliable. [1] Therefore, its existence must be checked
first.

[1]: https://learn.microsoft.com/en-us/windows/win32/api/shellapi/nf-shellapi-shfileoperationa

src/libs/portability/CMakeLists.txt

@@ -25,6 +25,10 @@ ENDIF(WIN32)
 # Note: Headers needed for having them available in IDEs.
 SD_ADD_LIBRARY(portability SHARED ${PORTABILITY_SOURCES} ${PORTABILITY_HEADERS})
 
+IF(WIN32)
+	TARGET_LINK_LIBRARIES(portability shlwapi)
+ENDIF()
+
 target_include_directories(portability PUBLIC
 	${CMAKE_BINARY_DIR}
 	${CMAKE_CURRENT_LIST_DIR}

src/libs/portability/win32/rmdir_r.cpp

@@ -13,10 +13,12 @@
 
 #include <windows.h>
 #include <winerror.h>
+#include <shlwapi.h>
 #include <shellapi.h>
 #include <cerrno>
 #include <cstddef>
 #include <cstdlib>
+#include <cstdint>
 #include <cstdio>
 #include <cstring>
 
@@ -45,10 +47,15 @@ failure:
 int portability::rmdir_r(const char *path)
 {
     int ret = -1, res;
-    char *dir = getdir(path);
     SHFILEOPSTRUCT op = {0};
+    char *dir = nullptr;
 
-    if (!dir)
+    if (!PathFileExistsA(path))
+    {
+        ret = 0;
+        goto end;
+    }
+    else if (!(dir = getdir(path)))
     {
         fprintf(stderr, "%s: getdir failed\n", __func__);
         goto end;