gprbuild from edge-testing is not installable due to missing shared lib

Looks like the last time this APK was updated it was built and linked against the libgnat 9.x shared libs, but the GCC toolchain has moved on to 10.x since then.

Steps to reproduce on Docker:

$ docker run --rm -it alpine:3.13 sh -l
90aca93851a0:/# echo "@edge-testing https://dl-cdn.alpinelinux.org/alpine/edge/testing" >> /etc/apk/repositories 
90aca93851a0:/# apk add gprbuild@edge-testing
fetch https://dl-cdn.alpinelinux.org/alpine/v3.13/main/x86_64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.13/community/x86_64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/edge/testing/x86_64/APKINDEX.tar.gz
ERROR: unable to select packages:
  so:libgnarl-9.so (no such package):
    required by: gprbuild-2019-r0[so:libgnarl-9.so]
  so:libgnat-9.so (no such package):
    required by: gprbuild-2019-r0[so:libgnat-9.so]

90aca93851a0:/# apk add libgnat
(1/2) Installing libgcc (10.2.1_pre1-r3)
(2/2) Installing libgnat (10.2.1_pre1-r3)
OK: 10 MiB in 16 packages

90aca93851a0:/# apk info -L libgnat
libgnat-10.2.1_pre1-r3 contains:
usr/lib/libgnarl-10.so
usr/lib/libgnat-10.so