Revert "guix: Build depends/qt with our platform definition"

This reverts commit dc4137a.

Author: hebasto

contrib/guix/libexec/build.sh

@@ -196,7 +196,6 @@ make -C depends --jobs="$JOBS" HOST="$HOST" \
                                    x86_64_linux_RANLIB=x86_64-linux-gnu-ranlib \
                                    x86_64_linux_NM=x86_64-linux-gnu-nm \
                                    x86_64_linux_STRIP=x86_64-linux-gnu-strip \
-                                   qt_config_opts_x86_64_linux='-platform linux-g++ -xplatform bitcoin-linux-g++' \
                                    FORCE_USE_SYSTEM_CLANG=1