MT#61185 debian/control: add missing pkg-config

>    dh_auto_build
> 	make -j6 "INSTALL=install --strip-program=true"
> make[1]: Entering directory '/build/ngcp-asterisk-voicemail-20.1.0+0~mr13.1.0.0+0~20241001083739.1186+bookworm~1.gbp169df5'
> make[1]: pkg-config: No such file or directory

Change-Id: I79f79517ae1673ffe06ce2502c3e34681ad3c067

debian/control

@@ -9,6 +9,7 @@ Build-Depends:
  asterisk-dev,
  debhelper-compat (= 13),
  libpcre2-dev,
+ pkgconf,
  quilt,
  unixodbc-dev,