Teuchos: Fix POSIX code in Teuchos::SystemInformation for Windows compilers

The WIN32 API includes a compatible counterpart to the POSIX functions introduced
in the commit referenced in the issue description (popen and pclose). The Windows
versions have the same parameters, return type, and behavior, but the function name
is different (_popen and _pclose).  There is also a correction to the return value
from the function std::filesystem::canonical, which is being assigned to a std::string
when the function returns a std::filesystem::path.

Author: hkthorn

packages/teuchos/core/src/Teuchos_SystemInformation.cpp

@@ -24,6 +24,14 @@
 // needs to be in the global namespace
 extern char **environ;
 #endif
+#if defined(_WIN32)
+#include <stdio.h>
+FILE *popen(const char *command, const char *mode)
+{ return _popen(command, mode); }
+
+int pclose(FILE *stream)
+{ return _pclose(stream);}
+#endif
 
 namespace Teuchos::SystemInformation {
 
@@ -213,7 +221,7 @@ void initializeCollection() {
 
 #if !defined(__GNUC__) || (__GNUC__ >= 10)
   try {
-    const std::string executable = std::filesystem::canonical("/proc/self/exe");
+    const std::string executable = std::filesystem::canonical("/proc/self/exe").string();
     if (!executable.empty()) {
       registerCommand("ldd", "ldd " + executable, "ldd");
     }