Add pre-requisite patch for musl (#2167)

The patches for hidden symbols, are applied to windows and musl, but we need a previous patch for this to apply cleanly.

Author: angerman

overlays/bootstrap.nix

@@ -265,9 +265,10 @@ in {
                 ++ final.lib.optional (versionAtLeast "9.0"                             && final.stdenv.targetPlatform.isAarch64) ./patches/ghc/ghc-9.0-aarch64-handle-none-rela.patch
                 ++ final.lib.optional (versionAtLeast "9.6.3"  && versionLessThan "9.6.4" && final.stdenv.targetPlatform.isWindows) ./patches/ghc/ghc-9.6-hadrian-splitsections.patch
                 ++ final.lib.optional (versionAtLeast "9.8.1"  && versionLessThan "9.9" && final.stdenv.targetPlatform.isWindows) ./patches/ghc/ghc-9.6-hadrian-splitsections.patch
-                # this patch was backported to 9.4.8
+                # this patch was backported to 9.4.8 and 9.6.4
                 ++ final.lib.optional (versionAtLeast "9.4"    && versionLessThan "9.4.8" && final.stdenv.targetPlatform.isWindows) ./patches/ghc/ghc-9.6-fix-code-symbol-jumps.patch
-                ++ final.lib.optional (versionAtLeast "9.6"    && versionLessThan "9.6.4" && final.stdenv.targetPlatform.isWindows) ./patches/ghc/ghc-9.6-fix-code-symbol-jumps.patch
+                # we also want to apply this to musl, so that the ./patches/ghc/ghc-9.6-0006-Adds-support-for-Hidden-symbols.patch applies.
+                ++ final.lib.optional (versionAtLeast "9.6"    && versionLessThan "9.6.4" && (final.stdenv.targetPlatform.isWindows || final.stdenv.targetPlatform.isMusl)) ./patches/ghc/ghc-9.6-fix-code-symbol-jumps.patch
                 ++ final.lib.optional (versionAtLeast "9.8"    && versionLessThan "9.9.20231203" && final.stdenv.targetPlatform.isWindows) ./patches/ghc/ghc-9.6-fix-code-symbol-jumps.patch
                 # this one is to allow linking extra symbols from iserv.
                 # ++ fromUntil "9.6.1" "9.10"                                                                                       ./patches/ghc/iserv-syms.patch