Passing CFLAGS=-fPIE to rust build system

I am building suricata6 for inclusion into OpenWrt. I am working to target arm, armv5, armv6, armv7, aarch64, mips, mipsel, mips64, mips64el, powerpc, powerpc64, and x86_64 (there might be others, but those are the ones on the top of my head). All of the targets do/will have their own Tier 3 rust-lang tuple as xxxx-openwrt-linux-musl, and rust-lang in the build system itself is already embedded.

In order build suricata6, I need to pass -fPIE to the rustc/cargo calls used by the suricata Makefile when building x86_64 targets, or it fails when I include --enable-pie. This, so far, has only manifested itself with the x86_64 targets. Mips64 compiles fine (and fails for other reasons related to Suricata which are currently being explored)

OpenWrt has user-land ASLR_PIE, but for whatever reason, this isn’t being passed to Suricata, so I’m looking to force it (or, disable --enable-pie for x86_64 targets).

I need to be able to invoke it from the make command, and would like to avoid adding patches to change files locally prior to running. Any suggestions on how to do this?