contrib: qt: fix string comparison

-eq is for comparing integers and prints errors like:

install_wrapper.sh: 27: [: Illegal number: imageformats

contrib/src/qt/install_wrapper.sh

@@ -24,7 +24,7 @@ fi
 pkgconfigdir="$(cd "$(dirname "${DEST}")" && pwd -P)"
 
 # Filter packages installed in a pkgconfig/ folder
-if [ "$(basename "${pkgconfigdir}")" -eq "pkgconfig" ]; then
+if [ "$(basename "${pkgconfigdir}")" = "pkgconfig" ]; then
     exit 0
 fi