Merge pull request swiftlang#76645 from swiftlang/lldb/ci-build-libcxx-linux-to-main

[utils][presets] Build libc++ for LLDB on linux

Author: Michael137

utils/build-presets.ini

@@ -3066,6 +3066,8 @@ mixin-preset=
     sourcekit_stress_test_mixin
 
 [preset: linux_lldb]
+# Build libcxx for tests
+libcxx
 lldb
 foundation
 libdispatch