pkgsrc: pkgconfig found no x11.pc

[spectre210]

Hallo Leute,
Ich habe pkgsrc in slackware installiert.
Zur Zeit versuche ich vlc zu compilieren, bricht jedoch immer mit:
checking for XV... configure: error: Package requirements (x11 xext xextproto videoproto) were not met:

No package 'x11' found
No package 'xext' found

Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.

Alternatively, you may set the environment variables XV_CFLAGS
and XV_LIBS to avoid the need to call pkg-config.
See the pkg-config man page for more details.

*** Error code 1

Stop.
bmake: stopped in /usr/pkgsrc/x11/libXv
WARNING: *** Please consider adding c++ to USE_LANGUAGES in the package Makefile.
WARNING: *** Please consider adding fortran to USE_LANGUAGES in the package Makefile.
*** Error code 1

Stop.
bmake: stopped in /usr/pkgsrc/x11/libXv
*** Error code 1

Stop.
bmake: stopped in /usr/pkgsrc/multimedia/vlc

ab.
Ich habe versucht, den PKG_CONFIG_PATH auf /usr/lib64/pkgconfig zu setzen.
Darin befindet sich die x11.pc und xext.pc.
Jedoch kein Erfolg.
Vielleicht wisst ihr mehr.
Vielen Dank von spectre210