boost: fix segfaults on ppc64

Fixes https://github.com/NixOS/nix/issues/2517

See also:
https://github.com/boostorg/context/issues/72
https://github.com/boostorg/fiber/issues/193

These issues have been resolved by:
https://github.com/boostorg/context/pull/106
https://github.com/boostorg/context/commit/d4608a4e8ba2e8a0bdd45613243e6c53a23d23dc
which is merged into boost as of v1.71.0.

This feature was introduced (with the bug) in
boost v1.61 and was fixed in v1.71. So we apply
the patch to all versions in that range.

pkgs/development/libraries/boost/generic.nix

@@ -1,4 +1,5 @@
 { stdenv, icu, expat, zlib, bzip2, python, fixDarwinDylibNames, libiconv
+, fetchpatch
 , which
 , buildPackages
 , toolset ? /**/ if stdenv.cc.isClang  then "clang"
@@ -113,6 +114,14 @@ stdenv.mkDerivation {
     if version == "1.55.0"
     then ./darwin-1.55-no-system-python.patch
     else ./darwin-no-system-python.patch)
+  # Fix boost-context segmentation faults on ppc64 due to ABI violation
+  ++ optional (versionAtLeast version "1.61" &&
+               versionOlder version "1.71") (fetchpatch {
+    url = "https://github.com/boostorg/context/commit/2354eca9b776a6739112833f64754108cc0d1dc5.patch";
+    sha256 = "067m4bjpmcanqvg28djax9a10avmdwhlpfx6gn73kbqqq70dnz29";
+    stripLen = 1;
+    extraPrefix = "libs/context/";
+  })
   ++ optional (and (versionAtLeast version "1.70") (!versionAtLeast version "1.73")) ./cmake-paths.patch
   ++ optional (versionAtLeast version "1.73") ./cmake-paths-173.patch;