Find zstd with pkg-config due to non-standard Homebrew installation o…

…n M1

Fixes #18

llvm.opam

@@ -23,6 +23,7 @@ depends: [
   "dune" {>= "2.7"}
   "ctypes" {>= "0.4"}
   "conf-llvm" {build & = version}
+  "conf-pkg-config"
 ]
 synopsis: "The OCaml bindings distributed with LLVM"
 description: "Note: LLVM should be installed first."

setup.sh

@@ -45,7 +45,9 @@ if test -z "$default_mode"; then
 fi
 
 base_cflags=$(llvm_config --cflags)
-ldflags="$(llvm_config --ldflags) -lstdc++"
+# pkg-config libzstd necessary because Homebrew installs it in nonconventional
+# location on Apple Silicon Macs
+ldflags="$(llvm_config --ldflags) -lstdc++ $(pkg-config libzstd --libs)"
 llvm_targets=$(llvm_config --targets-built)
 
 rm -rf src