From: hololeap <hololeap@protonmail.com>
Signed-off-by: hololeap <hololeap@protonmail.com>

doctests don't seem to work with Setup.hs

The hackage tarball doesn't include cabal.project which seems to be necessary
for doctest-parallel to work. Even when this file is copied to $S, Setup.hs
doesn't seem to recognize it.

The necessary flag is not recognized by `./setup configure`:
    --write-ghc-environment-files=always
See: <https://cabal.readthedocs.io/en/3.4/cabal-project.html#cfg-field-write-ghc-environment-files>

diff -urN regex-tdfa-1.3.2/regex-tdfa.cabal regex-tdfa-1.3.2-r1/regex-tdfa.cabal
--- regex-tdfa-1.3.2/regex-tdfa.cabal	2022-08-14 00:42:54.578227087 -0600
+++ regex-tdfa-1.3.2-r1/regex-tdfa.cabal	2022-08-14 00:43:17.428227098 -0600
@@ -175,6 +175,7 @@
     ghc-options:        -O2
 
 test-suite doctest
+  buildable:      False
   type:           exitcode-stdio-1.0
   hs-source-dirs: test
   main-is:        DocTestMain.hs