ci(sr.ht): Use RelWithDebInfo builds

Many compiler checks rely on optimizations being enabled, so we want
these to show up in CI.  Use RelWithDebInfo instead of Release so that
assert() statements aren't compiled out.

.builds/freebsd.yml

@@ -28,7 +28,7 @@ tasks:
     gmake deps
 - build: |
     cd neovim
-    gmake CMAKE_BUILD_TYPE=Release CMAKE_EXTRA_FLAGS="${CMAKE_EXTRA_FLAGS}" nvim
+    gmake CMAKE_BUILD_TYPE=RelWithDebInfo CMAKE_EXTRA_FLAGS="${CMAKE_EXTRA_FLAGS}" nvim
 - functionaltest: |
     cd neovim
     gmake functionaltest

.builds/openbsd.yml

@@ -28,16 +28,16 @@ tasks:
     mkdir neovim/.deps
     cd neovim/.deps
     cmake -G Ninja ../third-party/
-    cmake --build . --config Debug
+    cmake --build . --config RelWithDebInfo
 - build: |
     mkdir neovim/build
     cd neovim/build
     cmake -G Ninja $CMAKE_EXTRA_FLAGS ..
-    cmake --build . --config Debug
+    cmake --build . --config RelWithDebInfo
     ./bin/nvim --version
 - functionaltest: |
     cd neovim/build
-    cmake --build . --config Debug --target functionaltest
+    cmake --build . --config RelWithDebInfo --target functionaltest
 - oldtest: |
     cd neovim
     gmake oldtest