Add fs_gameDllPath to set additional directory to search game DLLs in

If set, it's searched before all other paths when laoding game libs
(mymod.dll, mymod.so, mymod.dylib, ...)

Useful when developing/testing mods

Author: DanielGibson

neo/framework/Common.cpp

@@ -2625,6 +2625,14 @@ Helper for LoadGameDLL() to make it less painful to try different dll names.
 =================
 */
 void idCommonLocal::LoadGameDLLbyName( const char *dll, idStr& s ) {
+	// try fs_dllpath first, if set
+	const char* dllpath = cvarSystem->GetCVarString("fs_gameDllPath");
+	if (dllpath != NULL && dllpath[0] != '\0') {
+		s = dllpath;
+		s.AppendPath(dll);
+		gameDLL = sys->DLL_Load(s);
+	}
+
 	s.CapLength(0);
 	#if defined(__AROS__)
 	// check in the launch (mod) directory first on AROS
@@ -2635,8 +2643,9 @@ void idCommonLocal::LoadGameDLLbyName( const char *dll, idStr& s ) {
 			return;
 	}
 	#endif
-	// try next to the binary
-	if (Sys_GetPath(PATH_EXE, s)) {
+
+	// try next to the binary second (build tree)
+	if (!gameDLL && Sys_GetPath(PATH_EXE, s)) {
 		// "s = " seems superfluous, but works around g++ 4.7 bug else StripFilename()
 		// (and possibly even CapLength()) seems to be "optimized" away and the string contains garbage
 		s = s.StripFilename();

neo/framework/FileSystem.cpp

@@ -415,6 +415,8 @@ class idFileSystemLocal : public idFileSystem {
 	static idCVar			fs_game_base;
 	static idCVar			fs_caseSensitiveOS;
 	static idCVar			fs_searchAddons;
+	// DG: additional directory to search for game DLLs
+	static idCVar			fs_gameDllPath;
 
 	backgroundDownload_t *	backgroundDownloads;
 	backgroundDownload_t	defaultBackgroundDownload;
@@ -483,6 +485,8 @@ idCVar	idFileSystemLocal::fs_caseSensitiveOS( "fs_caseSensitiveOS", "1", CVAR_SY
 #endif
 idCVar	idFileSystemLocal::fs_searchAddons( "fs_searchAddons", "0", CVAR_SYSTEM | CVAR_BOOL, "search all addon pk4s ( disables addon functionality )" );
 
+idCVar idFileSystemLocal::fs_gameDllPath( "fs_gameDllPath", "", CVAR_SYSTEM | CVAR_INIT, "additional directory to search the game .dll (.so/.dylib/...) in; searched before all other places (if set)" );
+
 idFileSystemLocal	fileSystemLocal;
 idFileSystem *		fileSystem = &fileSystemLocal;