mtxclient: fix compilation with olm-3.2.6

Patch adapted from upstream b452a984b0fc522c21bb8df7d320bf13960974d0,
which did not apply due to whitespace changes.

pkgs/development/libraries/mtxclient/default.nix

@@ -21,6 +21,9 @@ stdenv.mkDerivation rec {
     sha256 = "sha256-UKroV1p7jYuNzCAFMsuUsYC/C9AZ1D4rhwpwuER39vc=";
   };
 
+  # This patch should be obsolete and should stop applying the in next release.
+  patches = [ ./fix-compilation-with-olm-3.2.5.patch ];
+
   cmakeFlags = [
     # Network requiring tests can't be disabled individually:
     # https://github.com/Nheko-Reborn/mtxclient/issues/22

pkgs/development/libraries/mtxclient/fix-compilation-with-olm-3.2.5.patch

@@ -0,0 +1,22 @@
+diff -Naur old/lib/crypto/client.cpp c5pf6ygk9v9rdwwr3dyd24wghflp0vmx-source/lib/crypto/client.cpp
+--- old/lib/crypto/client.cpp	2021-10-22 19:31:52.159836190 +0300
++++ c5pf6ygk9v9rdwwr3dyd24wghflp0vmx-source/lib/crypto/client.cpp	2021-10-22 19:30:42.882010441 +0300
+@@ -37,15 +37,15 @@
+ 
+ };
+ 
+-OlmErrorCode
++mtx::crypto::OlmErrorCode
+ olm_exception::ec_from_string(std::string_view error)
+ {
+         for (size_t i = 0; i < olmErrorStrings.size(); i++) {
+                 if (olmErrorStrings[i] == error)
+-                        return static_cast<OlmErrorCode>(i);
++			return static_cast<mtx::crypto::OlmErrorCode>(i);
+         }
+ 
+-        return OlmErrorCode::UNKNOWN_ERROR;
++        return mtx::crypto::OlmErrorCode::UNKNOWN_ERROR;
+ }
+ 
+ void