main/systemd-boot: enable armv7 and riscv64 support (MR 4830)

[ci:skip-build] already built successfully in CI
[ci:skip-vercheck]

main/systemd-boot/APKBUILD

@@ -21,7 +21,7 @@ url="https://systemd.io/"
 # armv7: untested
 # riscv64: untested
 # x86: untested (and unnecessary?)
-arch="x86_64 aarch64"
+arch="aarch64 armv7 riscv64 x86_64"
 license="GPL-2.0-only"
 # Some of these are just to satisfy systemd's meson config, and aren't actually
 # used for building the boot manager or stub...