codegen: Pass --installdir flag to cabal install (#249)

In some configurations, 'cabal install' will install the binary
into the current directory instead of in the global directory
on 'PATH', which can cause the haskell step to fail. Pass
the --installdir flag to avoid that.

Author: varungandhi-src

dev/proto-generate.sh

@@ -19,8 +19,9 @@ fi
 
 echo "--- Haskell ---"
 command -v cabal > /dev/null 2>&1 || { echo >&2 "Haskell's 'cabal' command is not installed. Please install it first via https://www.haskell.org/ghcup/"; exit 1; }
-cabal install proto-lens-protoc-0.7.1.1 ghc-source-gen-0.4.3.0 --overwrite-policy=always --ghc-options='-j2 +RTS -A32m'
-ln -sfv `which proto-lens-protoc` "$PWD/.bin/protoc-gen-haskell"
+cabal install proto-lens-protoc-0.7.1.1 ghc-source-gen-0.4.3.0 --overwrite-policy=always --ghc-options='-j2 +RTS -A32m' --installdir="$PWD/.bin"
+# buf requires the generator to be named protoc-gen-*
+ln -sfv "$PWD/.bin/proto-lens-protoc" "$PWD/.bin/protoc-gen-haskell"
 PATH="$PWD/.bin:$PATH"
 
 echo "--- buf ---"