PresetUpdater: Use PID in cache tmp filenames

xs/src/libslic3r/Utils.hpp

@@ -62,6 +62,9 @@ extern std::string timestamp_str();
 // to be placed at the top of Slic3r generated files.
 inline std::string header_slic3r_generated() { return std::string("generated by " SLIC3R_FORK_NAME " " SLIC3R_VERSION " " ) + timestamp_str(); }
 
+// getpid platform wrapper
+extern unsigned get_current_pid();
+
 // Compute the next highest power of 2 of 32-bit v
 // http://graphics.stanford.edu/~seander/bithacks.html
 template<typename T>

xs/src/libslic3r/utils.cpp

@@ -1,6 +1,12 @@
 #include <locale>
 #include <ctime>
 
+#ifdef WIN32
+#include <windows.h>
+#else
+#include <unistd.h>
+#endif
+
 #include <boost/log/core.hpp>
 #include <boost/log/trivial.hpp>
 #include <boost/log/expressions.hpp>
@@ -271,4 +277,13 @@ std::string timestamp_str()
     return buf;
 }
 
+unsigned get_current_pid()
+{
+#ifdef WIN32
+    return GetCurrentProcessId();
+#else
+    return ::getpid();
+#endif
+}
+
 }; // namespace Slic3r