xbps-src: multiple performance improvements

- use xbps-checkvers(1) to resolve dependencies.
- all dependencies are installed at once for the host and target.
- the show-build-deps target is now much faster.
- the update-bulk/show-repo-updates targets are now much faster.
- the update-sys/show-sys-updates targets are now much faster.
- the bootstrap target now works on musl hosts.
- simplified some loops.
- use cut(1) rather than awk(1) where applicable.
- multiple random changes to improve performance.

Based on work started by @Duncaen on #12433

Close #12433
Close #11282

common/hooks/do-pkg/00-gen-pkg.sh

@@ -32,16 +32,16 @@ genpkg() {
 
 	_preserve=${preserve:+-p}
 	if [ -s ${PKGDESTDIR}/rdeps ]; then
-		_deps="$(cat ${PKGDESTDIR}/rdeps)"
+		_deps="$(<${PKGDESTDIR}/rdeps)"
 	fi
 	if [ -s ${PKGDESTDIR}/shlib-provides ]; then
-		_shprovides="$(cat ${PKGDESTDIR}/shlib-provides)"
+		_shprovides="$(<${PKGDESTDIR}/shlib-provides)"
 	fi
 	if [ -s ${PKGDESTDIR}/shlib-requires ]; then
-		_shrequires="$(cat ${PKGDESTDIR}/shlib-requires)"
+		_shrequires="$(<${PKGDESTDIR}/shlib-requires)"
 	fi
 	if [ -s ${XBPS_STATEDIR}/gitrev ]; then
-		_gitrevs="$(cat ${XBPS_STATEDIR}/gitrev)"
+		_gitrevs="$(<${XBPS_STATEDIR}/gitrev)"
 	fi
 
 	# Stripping whitespaces