fix(libc): return fclose failures to callers

(cherry picked from commit 610d6cdda098e9adfcd3814b52f8eba01caaa4d1)

core/libs/prx/libc/include/FileStream.hpp

@@ -122,11 +122,12 @@ public:
         SyncStatus();
     }
 
-    void Close() {
+    int Close() {
         GetHandle();
-        if (std::fclose(std::exchange(_handle, nullptr)) != 0) throw std::runtime_error("FileStream: close failed");
+        const int result = std::fclose(std::exchange(_handle, nullptr));
         _guest.flags = 0;
         _guest.descriptor = -1;
+        return result;
     }
 };
 static_assert(std::is_standard_layout_v<FileStream>);

core/libs/prx/libc/src/FileAndHeap.cpp

@@ -146,8 +146,7 @@ int APS5_VABI fopen_s_nid_postfix(FileStream** result, const char* filename, con
 int APS5_VABI fclose_nid_postfix(FileStream* stream) {
     GetNativeStream(stream);
     std::unique_ptr<FileStream> owner(stream->IsDynamic() ? stream : nullptr);
-    stream->Close();
-    return 0;
+    return stream->Close();
 }
 
 int APS5_VABI fseek_nid_postfix(FileStream* stream, std::int64_t offset, int origin);

core/libs/tests/GuestFiopen.cpp

@@ -131,6 +131,14 @@ int main() {
     Require(stream != nullptr && std::fgetc(stream->GetHandle()) == 'k');
     fclose_nid_postfix(stream);
 
+#ifndef _WIN32
+    auto* full = std::fopen("/dev/full", "wb");
+    Require(full != nullptr);
+    auto* fullStream = new FileStream(full, true);
+    Require(std::fwrite("buffered", 1, 8, full) == 8);
+    Require(fclose_nid_postfix(fullStream) == EOF);
+#endif
+
     std::filesystem::remove_all(dir);
     return 0;
 }