Linux: add ${CMAKE_DL_LIBS} to libHttpClient.Linux and WebSocketCompressionTests target_link_libraries

[armahnii2000]

Both targets transitively call dlfcn functions (via OpenSSL's dso_dlfcn.c) but don't link against libdl. On linkers that don't auto-resolve, the link fails:

/usr/bin/ld: dso_dlfcn.c:(.text+0xda): undefined reference to `dlerror'

Adds ${CMAKE_DL_LIBS} to:

• libHttpClient.Linux (shared lib) target_link_libraries
• WebSocketCompressionTests.Linux target_link_libraries

${CMAKE_DL_LIBS} is the idiomatic CMake variable for this — it expands to dl on platforms that need it and is empty elsewhere. Safe no-op on Windows/macOS.

Surfaced via the PlayFab.SDKs.All.TestDrop Linux pipeline.

[armahnii2000]

Pinging for review — would appreciate eyes from anyone with libHttpClient.Linux context:

• @jasonsandlin
• @SebastianPD
• @ScottMunroMS
• @rgomez391

Fix is a 2-line CMake change adding ${CMAKE_DL_LIBS} to two target_link_libraries blocks. Currently blocking the PlayFab.SDKs.All.TestDrop Linux pipeline (tracked in PlayFab work items 62492001 and 62492286).

[rgomez391]

Let's wait for the CI checks to pass before merging

[armahnii2000]

Closing this PR — the consumer side (Microsoft Xbox PlayFab.SDKs.All TestDrop pipeline) that motivated this fix is migrating its Linux build agent from Ubuntu 20.04 (glibc 2.31, clang-10) to Ubuntu 22.04 (glibc 2.35, clang-14). On glibc 2.35 the dl* symbols are merged into libc.so, so the link succeeds without an explicit -ldl (or ${CMAKE_DL_LIBS}).

Verified empirically: lab build 148767526 ran the unpatched Build/libHttpClient.Linux/CMakeLists.txt on Ubuntu 22.04 + clang-14 + glibc 2.35; both libHttpClient.Linux.so and WebSocketCompressionTests.Linux linked cleanly.

The fix is still correct on its merits for anyone building libHttpClient on older glibc — feel free to re-open / cherry-pick if useful — but our specific consumer no longer needs it. Apologies for the noise!