fix: print dlerror if dlopen fails (deepmodeling#4485)

xref: deepmodeling/deepmd-gnn#44

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
- Enhanced error messages for library loading failures on non-Windows
platforms.
- Updated thread management environment variable checks for improved
compatibility.
- Added support for mixed types in tensor input handling, allowing for
more flexible configurations.

- **Bug Fixes**
	- Improved error reporting for dynamic library loading issues.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
(cherry picked from commit cfe17a3)

source/api_cc/src/common.cc

@@ -389,7 +389,13 @@ static inline void _load_library_path(std::string dso_path) {
   if (!dso_handle) {
     throw deepmd::deepmd_exception(
         dso_path +
-        " is not found! You can add the library directory to LD_LIBRARY_PATH");
+        " is not found or fails to load! You can add the library directory to "
+        "LD_LIBRARY_PATH."
+#ifndef _WIN32
+        " Error message: " +
+        std::string(dlerror())
+#endif
+    );
   }
 }
 

source/lib/src/gpu/cudart/cudart_stub.cc

@@ -25,6 +25,10 @@ void *DP_cudart_dlopen(char *libname) {
 #endif
     if (!dso_handle) {
       std::cerr << "DeePMD-kit: Cannot find " << libname << std::endl;
+#ifndef _WIN32
+      std::cerr << "DeePMD-kit: Error message: " << std::string(dlerror())
+                << std::endl;
+#endif
       return nullptr;
     }
     std::cerr << "DeePMD-kit: Successfully load " << libname << std::endl;