build: let a failed pin check decide the exit status everywhere

fd627b1's message said the rewrite hardened a pin check that used `;`
where it needed `&&`. It hardened one of four. Three recipes still
ended their chain with `echo "==> ... done"; ` after a semicolon, so a
mismatched pin failed the `test`, skipped every build step, and then
ran the echo anyway -- exit 0, and make announced a pinned dependency
that nothing had verified. deps-windows also had the same break after
mkdir and after `make randomx`.

The one the earlier message did not mention is deps-secp256k1, on the
Linux path: libsecp256k1 is signature verification, so that was the
worst of the three to leave reporting success on an unverified
checkout.

Joined each chain with && the whole way to the closing echo, in
deps-secp256k1, and in both halves of deps-windows.

Verified by extracting each recipe as make expands it, splitting it
into logical recipe lines and running each in its own shell the way
make does, with git reporting a sha that does not match the pin: all
three previously exited 0 and now exit 1, and each deps-windows half
fails independently rather than relying on the other. With a matching
sha the recipes still exit 0, still print "done", and still write the
marker. The Windows path was not executed -- there is no MSYS2 here --
so pacman was shimmed and only the shell logic below it was measured.

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