Transition to new build command for libadalang and langkit

Closes eng/ide/ada_language_server#1591

Author: eliericha

subprojects/libadalang.toml

@@ -16,7 +16,7 @@ GPR_PROJECT_PATH.prepend = "${CRATE_ROOT}/build"
 type = "pre-build"
 # It is necessary to load the env here because macOS protection prevents
 # inheriting DYLD_LIBRARY_PATH from the parent environment
-command = ["bash", "-c", "-x", "source setenv.sh; pip install -rrequirements-{github,pypi}.txt && python manage.py generate"]
+command = ["bash", "-c", "-x", "source setenv.sh; pip install -rrequirements-{github,pypi}.txt && python -m langkit.scripts.lkm generate"]
 
 [[depends-on]]
 gnatcoll = "^24"