perl: add PACKAGECONFIG for db

perl-cross makes it easy to cleanly disable the use of Berkeley DB if desired,
so add a PACKAGECONFIG for this.

More of the dependencies (such as gdbm) can be controlled in the same way, but
Berkeley DB is a prime contender: it's a large library which we have to ship an
old release for due to licensing issues, so there are users who may want to
strip it out of builds entirely.

(From OE-Core rev: e3860098dadd0b1db97fb0414aae6abfc234b245)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/perl/perl_5.30.0.bb

@@ -35,10 +35,13 @@ S = "${WORKDIR}/perl-${PV}"
 
 inherit upstream-version-is-even
 
-DEPENDS += "db gdbm zlib virtual/crypt"
+DEPENDS += "gdbm zlib virtual/crypt"
 
 PERL_LIB_VER = "${@'.'.join(d.getVar('PV').split('.')[0:2])}.0"
 
+PACKAGECONFIG ??= "bdb"
+PACKAGECONFIG[bdb] = ",-Ui_db,db"
+
 # Don't generate comments in enc2xs output files. They are not reproducible
 export ENC2XS_NO_COMMENTS = "1"
 
@@ -56,7 +59,8 @@ do_configure_class-target() {
     -Duseshrplib \
     -Dsoname=libperl.so.5 \
     -Dvendorprefix=${prefix} \
-    -Darchlibexp=${STAGING_LIBDIR}/perl5/${PV}/${TARGET_ARCH}-linux
+    -Darchlibexp=${STAGING_LIBDIR}/perl5/${PV}/${TARGET_ARCH}-linux \
+    ${PACKAGECONFIG_CONFARGS}
 
     #perl.c uses an ARCHLIB_EXP define to generate compile-time code that
     #adds the archlibexp path to @INC during run-time initialization of a
@@ -79,7 +83,8 @@ do_configure_class-nativesdk() {
     -Duseshrplib \
     -Dsoname=libperl.so.5 \
     -Dvendorprefix=${prefix} \
-    -Darchlibexp=${STAGING_LIBDIR}/perl5/${PV}/${TARGET_ARCH}-linux
+    -Darchlibexp=${STAGING_LIBDIR}/perl5/${PV}/${TARGET_ARCH}-linux \
+    ${PACKAGECONFIG_CONFARGS}
 
     # See the comment above
     sed -i -e "s,${STAGING_LIBDIR},${libdir},g" config.h
@@ -91,7 +96,8 @@ do_configure_class-native() {
     -Duseshrplib \
     -Dsoname=libperl.so.5 \
     -Dvendorprefix=${prefix} \
-    -Ui_xlocale
+    -Ui_xlocale \
+    ${PACKAGECONFIG_CONFARGS}
 }
 
 do_configure_append() {