rts: Depend explicitly on libcwip/T19029

As noted in #19029, currently `ghc-prim` explicitly lists `libc` in
`extra-libraries`, resulting in incorrect link ordering with the
`extra-libraries: pthread` in `libHSrts`. Fix this by adding an explicit
dependency on `libc` to `libHSrts`.

Closes #19029.

1 files changed, 6 insertions, 0 deletions

diff --git a/rts/rts.cabal.in b/rts/rts.cabal.in
index 0b57c290bf..9e998bb911 100644
--- a/rts/rts.cabal.in
+++ b/rts/rts.cabal.in
@@ -109,6 +109,12 @@ library
 
     exposed: True
     exposed-modules:
+    if os(linux)
+       -- the RTS depends upon libc. while this dependency is generally
+       -- implicitly added by `cc`, we must explicitly add it here to ensure
+       -- that it is ordered correctly with libpthread, since ghc-prim.cabal
+       -- also explicitly lists libc. See #19029.
+       extra-libraries: c
     if flag(libm)
        -- for ldexp()
        extra-libraries: m