qtractor compile error with current (15.0 RC1)

Hello there

I start to migrating to slackware-15.0 RC1 and checking some software. I can't compile qtractor-0.9.24

error is:
Code:/usr/bin/ld: .obj/qtractorPlugin.o: undefined reference to symbol 'dlclose@@GLIBC_2.2.5'
/usr/bin/ld: /lib64/libdl.so.2: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
make[2]: *** [Makefile:923: qtractor] Error 1used this SlackBuild.

Added qt5 dir (success) and tried to add -ldl (fail).

Code:CMAKE_DL_LIBS="-ldl" \ # 1st attempt
CFLAGS="$SLKCFLAGS" \
CXXFLAGS="$SLKCFLAGS" \
./configure \
LIBS=-ldl \ # 2nd attempt
--prefix=/usr \
--libdir=/usr/lib${LIBDIRSUFFIX} \
--sysconfdir=/etc \
--localstatedir=/var \
--mandir=/usr/man \
--with-qt=/usr/lib${LIBDIRSUFFIX}/qt5 \ # success
--build=$ARCH-slackware-linuxDependencies are installed (jack and ladspa_sdk). But the problem is somewhere else.

Maybe useful links CMAKE_DL_LIBS, set.

Funny thing. After SlackBuild fails I edited `src/Makefile` (unavailable before `make`) to add after `-lpthread` the `-ldl` and qtractor executable is created!

But what is the right option for a proper SlackBuild?