Use unsafeThawByteArray# once available

[ˌbodʲɪˈɡrʲim]

See GHC MR https://gitlab.haskell.org/ghc/ghc/-/merge_requests/9739

unsafeThawByteArray# should be used instead of unsafeCoerce#:

linear-builder/src/Data/Text/Builder/Linear/Core.hs

Lines 261 to 263 in 38c3587

 unsafeThaw ∷ Array → ST s (MArray s) 
 unsafeThaw (ByteArray a) = ST $ \s# → 
   (# s#, MutableByteArray (unsafeCoerce# a) #)