set C/LDFLAGS for complement dependencies directly

Previously we were relying on NIX_CFLAGS_COMPILE, but this is not being
set in static devshells. A cleaner solution for complement would likely
be to build the tests in their own nix derivation instead of building
them in the devshell, but this change unblocks CI for now.

flake.nix

@@ -56,6 +56,10 @@
           # Convenient way to access a pinned version of Complement's source
           # code.
           COMPLEMENT_SRC = inputs.complement.outPath;
+
+          # Needed for Complement
+          CGO_CFLAGS = "-I${scope.pkgs.olm}/include";
+          CGO_LDFLAGS = "-L${scope.pkgs.olm}/lib";
         };
 
         # Development tools
@@ -77,7 +81,6 @@
 
           # Needed for Complement
           go
-          olm
 
           # Needed for our script for Complement
           jq