xbps-src: detect two types of build loops and abort()

- depends on itself
- dep depends on targetpkg

common/xbps-src/shutils/build_dependencies.sh

@@ -217,13 +217,13 @@ install_pkg_deps() {
     # Host build dependencies.
     #
     for i in ${host_build_depends}; do
+        _realpkg=$($XBPS_UHELPER_CMD getpkgname "$i" 2>/dev/null)
         check_pkgdep_matched "$i" version
         local rval=$?
         if [ $rval -eq 0 ]; then
             echo "   [host] ${i}: installed."
             continue
         elif [ $rval -eq 1 ]; then
-            _realpkg="$($XBPS_UHELPER_CMD getpkgname $i 2>/dev/null)"
             iver=$($XBPS_UHELPER_CMD version ${_realpkg})
             if [ $? -eq 0 -a -n "$iver" ]; then
                 echo "   [host] ${i}: installed $iver (virtualpkg)."
@@ -240,6 +240,11 @@ install_pkg_deps() {
                 continue
             else
                 echo "   [host] ${i}: not found."
+                if [ "${_realpkg}" = "$targetpkg" ]; then
+                    msg_error "${pkg}: [host] build loop detected: ${_realpkg} <-> ${targetpkg} [depends on itself]\n"
+                elif [ "${_realpkg}" = "$pkg" ]; then
+                    msg_error "${pkg}: [host] build loop detected: $pkg <-> ${_realpkg}\n"
+                fi
             fi
         fi
         host_missing_deps+=("${i}")
@@ -249,13 +254,13 @@ install_pkg_deps() {
     # Host check dependencies.
     #
     for i in ${host_check_depends}; do
+        _realpkg="$($XBPS_UHELPER_CMD getpkgname $i 2>/dev/null)"
         check_pkgdep_matched "$i" version
         local rval=$?
         if [ $rval -eq 0 ]; then
             echo "   [check] ${i}: installed."
             continue
         elif [ $rval -eq 1 ]; then
-            _realpkg="$($XBPS_UHELPER_CMD getpkgname $i 2>/dev/null)"
             iver=$($XBPS_UHELPER_CMD version ${_realpkg})
             if [ $? -eq 0 -a -n "$iver" ]; then
                 echo "   [check] ${i}: installed $iver (virtualpkg)."
@@ -272,6 +277,11 @@ install_pkg_deps() {
                 continue
             else
                 echo "   [check] ${i}: not found."
+                if [ "${_realpkg}" = "$targetpkg" ]; then
+                    msg_error "${pkg}: [check] build loop detected: ${_realpkg} <-> ${targetpkg} [depends on itself]!\n"
+                elif [ "${_realpkg}" = "$pkg" ]; then
+                    msg_error "${pkg}: [check] build loop detected: $pkg <-> ${_realpkg}\n"
+                fi
             fi
         fi
         check_missing_deps+=("${i}")
@@ -311,6 +321,11 @@ install_pkg_deps() {
                 continue
             else
                 echo "   [target] ${i}: not found."
+                if [ "${_realpkg}" = "$targetpkg" ]; then
+                    msg_error "${pkg}: [target] build loop detected: ${_realpkg} <-> ${targetpkg} [depends on itself]\n"
+                elif [ "${_realpkg}" = "$pkg" ]; then
+                    msg_error "${pkg}: [target] build loop detected: $pkg <-> ${_realpkg}\n"
+                fi
             fi
         fi
         missing_deps+=("${i}")
@@ -368,6 +383,11 @@ install_pkg_deps() {
                 echo "   [runtime] ${_realpkg}: not found."
             fi
         fi
+        if [ "${_realpkg}" = "$targetpkg" ]; then
+            msg_error "${pkg}: [run] build loop detected: ${_realpkg} <-> ${targetpkg} [depends on itself]\n"
+        elif [ "${_realpkg}" = "$pkg" ]; then
+            msg_error "${pkg}: [run] build loop detected: $pkg <-> ${_realpkg}\n"
+        fi
         missing_rdeps+=("${_realpkg}")
     done
 
@@ -414,6 +434,7 @@ install_pkg_deps() {
     for i in ${missing_deps[@]}; do
         # packages not found in repos, install from source.
         (
+
         curpkgdepname=$($XBPS_UHELPER_CMD getpkgname "$i" 2>/dev/null)
         setup_pkg $curpkgdepname $cross
         exec env XBPS_DEPENDENCY=1 XBPS_BINPKG_EXISTS=1 \