fp6-vendor-blobs: the checksum the extractor change forgot, and a check that finds the next one in a second

CI run 52 failed at minute 57 with `fp6-vendor-blobs-extract: FAILED` from
abuild's checksum verification: 9575e55 changed the extractor and left its
sha512sums entry alone. Nothing was installed or published; latest is the
run-51 image.

Fix the sum, and stop paying an hour to learn it. check-aports.sh sources
every APKBUILD under aports/ and compares the committed sha512sums of its
local source files (scripts, units, configs, patches, including ones in a
subdirectory) against the files themselves. build.sh runs it before
pmbootstrap touches anything, so this class of mistake now fails in the first
seconds of a run and prints the line to paste. Aports whose sums build.sh
regenerates with pmbootstrap checksum are read from build.sh and skipped, so
the two lists cannot drift.

Verified: the checker reports exactly the run-52 mismatch on the tree as
pushed and nothing on the tree as fixed; a scratch copy with one corrupted
sum is caught; the fixed aport builds under abuild in an alpine:edge
container (the only complaint was the throwaway signing key at the index
step, which the CI's pmbootstrap flow does not have).

build.sh

@@ -47,6 +47,11 @@ FPD_SHA256="
 PMAPORTS_REPO=https://gitlab.postmarketos.org/postmarketOS/pmaports.git
 
 cd "$(dirname "$0")"
+# Fail in seconds, not at minute 57: a stale sha512sum in one of our own
+# aports (run 52, fp6-vendor-blobs 1-r2) only surfaces when abuild reaches that
+# aport, an hour into the run. This checks every aport's local source files
+# against the committed sums before pmbootstrap does anything.
+./check-aports.sh
 
 # pmbootstrap refuses to run as root: install deps, then re-exec as a build
 # user with passwordless sudo (pmbootstrap escalates itself where needed).