dist: prefix from environment

These are baked in, so make them configurable for the build.

Signed-off-by: Ophestra <cat@gensokyo.uk>

dist/release.sh

@@ -1,6 +1,7 @@
 #!/bin/sh -e
 cd "$(dirname -- "$0")/.."
 VERSION="${HAKUREI_VERSION:-untagged}"
+prefix="${PREFIX:-/usr}"
 pname="hakurei-${VERSION}-$(go env GOARCH)"
 out="${DESTDIR:-dist}/${pname}"
 
@@ -15,9 +16,9 @@ go generate ./...
 go build -trimpath -v -o "${out}/bin/" -ldflags "-s -w
   -buildid= -linkmode external -extldflags=-static
   -X hakurei.app/internal/info.buildVersion=${VERSION}
-  -X hakurei.app/internal/info.hakureiPath=/usr/bin/hakurei
-  -X hakurei.app/internal/info.hsuPath=/usr/bin/hsu
-  -X main.hakureiPath=/usr/bin/hakurei" ./...
+  -X hakurei.app/internal/info.hakureiPath=${prefix}/bin/hakurei
+  -X hakurei.app/internal/info.hsuPath=${prefix}/bin/hsu
+  -X main.hakureiPath=${prefix}/bin/hakurei" ./...
 echo
 
 echo '# Testing hakurei.'