setFullGameExePath: Use ALTEXEPATH if defined over CUSTOMCMD path

steamtinkerlaunch

@@ -9132,8 +9132,10 @@ function ShaderRepoDialog {
 
 function setFullGameExePath {
 	if [[ ( "$USECUSTOMCMD" -eq 1 && -f "$CUSTOMCMD" && "$CUSTOMCMDRESHADE" -eq 1 ) || "$ONLY_CUSTOMCMD" -eq 1 ]]; then
-		FGEP="${CUSTOMCMD%/*}"
-
+		# Use Alternative EXE Path if defined instead of custom command path
+		# We should only use the custom command directory if no alternatiive EXE path is defined, and
+		# we should prioritise the alt path if it is defined
+		FGEP="${DEFINEDALTEXEPATH:-${CUSTOMCMD%/*}}"
 		writelog "INFO" "${FUNCNAME[0]} - Using the directory '$FGEP' of the used custom command as absolute game exe path"
 
 		if [ "$CUSTOMCMDRESHADE" -eq 1 ]; then
@@ -9582,9 +9584,7 @@ function installRSdll {
 function installReshade {
 	if [ "$USERESHADE" -eq 1 ]; then
 		prepareReshadeFiles
-		# setShadDestDir
-		# Use setShaderDest to avoid overwriting ALTEXEPATH if defined
-		setShaderDest
+		setShadDestDir  # Have to use setShadDestDir because setShadDest will use ABSGAMEEXEPATH which is not Custom Command 
 
 		INSTDESTDIR="$SHADDESTDIR"