adguardhome: add fail_arch

Author: miwu04

app-web/adguardhome/autobuild/defines

@@ -4,3 +4,7 @@ PKGDES="Network-level advertisement and tracker blocking DNS server"
 PKGDEP="glibc"
 BUILDDEP="go nodejs"
 ABTYPE=gomod
+# FIXME: Build fails due to SV39 limitation on SG2042 build hosts.
+#
+# RangeError: WebAssembly.instantiate(): Out of memory: Cannot allocate Wasm memory for new instance
+FAIL_ARCH="riscv64"