Pass plugin path around instead of redetecting

This is now set only once at the top level. This is needed for the
chainloading to work because we'll need to set the path when we create
the bridge.

src/common/linking.cpp

@@ -20,7 +20,9 @@
 
 #include <dlfcn.h>
 
-std::string get_this_file_location() {
+namespace fs = ghc::filesystem;
+
+fs::path get_this_file_location() {
     // We'll try to find the library this function was defined in. When called
     // from a copy of `libyabridge-*.so` this will return that library. Because
     // the chainloader libraries load the plugin libraries from fixed locations,