folly: add patch to install the test certificates

pkgs/by-name/fo/folly/install-test-certs.patch

@@ -0,0 +1,18 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index ecc11a7961..67a2b82b4b 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -489,8 +489,12 @@
+   ${FOLLY_DIR}/test/DeterministicSchedule.cpp
+   ${FOLLY_DIR}/json/JsonTestUtil.cpp
+ )
++auto_sources(test_certs "*.pem" "${FOLLY_DIR}/io/async/test/certs")
++install(FILES ${test_certs}
++  DESTINATION "${LIB_INSTALL_DIR}/folly/test-certs"
++)
+ target_compile_definitions(folly_test_util PUBLIC
+-  FOLLY_CERTS_DIR="${FOLLY_DIR}/io/async/test/certs"
++  FOLLY_CERTS_DIR="${LIB_INSTALL_DIR}/folly/test-certs"
+ )
+ set_property(TARGET folly_test_util PROPERTY VERSION ${PACKAGE_VERSION})
+ target_link_libraries(folly_test_util

pkgs/by-name/fo/folly/package.nix

@@ -129,6 +129,11 @@ stdenv.mkDerivation (finalAttrs: {
   dontUseNinjaCheck = true;
 
   patches = [
+    # Install the certificate files used by `libfolly_test_util` rather
+    # than leaving a dangling reference to the build directory in the
+    # `dev` output’s CMake files.
+    ./install-test-certs.patch
+
     # The base template for std::char_traits has been removed in LLVM 19
     # https://releases.llvm.org/19.1.0/projects/libcxx/docs/ReleaseNotes.html
     ./char_traits.patch