Add GETDEPS_CABAL_FLAGS env var

Summary:
X-link: facebookincubator/zstrong#871

The problem I need to solve is that projects without a pkg-config
can't be found by Cabal. I need to pass extra flags to Cabal for it to
find the includes and libraries for these projects. So here I'm
creating a `GETDEPS_CABAL_FLAGS` env with all the necessary flags.

It's a bit horrible. Really I want to do this only for the direct
deps, but where the env is being setup we don't have access to the
direct vs. non-direct deps currently, only the install_dirs.

Reviewed By: josefs

Differential Revision: D58200841

fbshipit-source-id: 03f8630610691485561438d69fe8e1182396cd04

build/fbcode_builder/getdeps/buildopts.py

@@ -340,14 +340,17 @@ def add_prefix_to_env(
     ) -> bool:  # noqa: C901
         bindir = os.path.join(d, "bin")
         found = False
+        has_pkgconfig = False
         pkgconfig = os.path.join(d, "lib", "pkgconfig")
         if os.path.exists(pkgconfig):
             found = True
+            has_pkgconfig = True
             add_path_entry(env, "PKG_CONFIG_PATH", pkgconfig, append=append)
 
         pkgconfig = os.path.join(d, "lib64", "pkgconfig")
         if os.path.exists(pkgconfig):
             found = True
+            has_pkgconfig = True
             add_path_entry(env, "PKG_CONFIG_PATH", pkgconfig, append=append)
 
         add_path_entry(env, "CMAKE_PREFIX_PATH", d, append=append)
@@ -369,6 +372,15 @@ def add_prefix_to_env(
                 add_flag(env, "CPPFLAGS", f"-I{ncursesincludedir}", append=append)
             elif "/bz2-" in d:
                 add_flag(env, "CPPFLAGS", f"-I{includedir}", append=append)
+            # For non-pkgconfig projects Cabal has no way to find the includes or
+            # libraries, so we provide a set of extra Cabal flags in the env
+            if not has_pkgconfig:
+                add_flag(
+                    env,
+                    "GETDEPS_CABAL_FLAGS",
+                    f"--extra-include-dirs={includedir}",
+                    append=append,
+                )
 
             # The thrift compiler's built-in includes are installed directly to the include dir
             includethriftdir = os.path.join(d, "include", "thrift")
@@ -407,6 +419,13 @@ def add_prefix_to_env(
                         add_flag(env, "LDFLAGS", f"-L{libdir}", append=append)
                     if add_library_path:
                         add_path_entry(env, "LIBRARY_PATH", libdir, append=append)
+                    if not has_pkgconfig:
+                        add_flag(
+                            env,
+                            "GETDEPS_CABAL_FLAGS",
+                            f"--extra-lib-dirs={libdir}",
+                            append=append,
+                        )
 
         # Allow resolving binaries (eg: cmake, ninja) and dlls
         # built by earlier steps