guix: remove errant leftover from #29648

We no longer build a lib, so a non-existent dir is causing builds to
fail.

contrib/guix/libexec/build.sh

@@ -321,12 +321,6 @@ mkdir -p "$DISTSRC"
     (
         cd installed
 
-        case "$HOST" in
-            *mingw*)
-                mv --target-directory="$DISTNAME"/lib/ "$DISTNAME"/bin/*.dll
-                ;;
-        esac
-
         # Prune libtool and object archives
         find . -name "lib*.la" -delete
         find . -name "lib*.a" -delete
@@ -340,7 +334,6 @@ mkdir -p "$DISTSRC"
                 # Split binaries and libraries from their debug symbols
                 {
                     find "${DISTNAME}/bin" -type f -executable -print0
-                    find "${DISTNAME}/lib" -type f -print0
                 } | xargs -0 -P"$JOBS" -I{} "${DISTSRC}/contrib/devtools/split-debug.sh" {} {} {}.dbg
                 ;;
         esac