cmake: Fix dependency problem

For normal builds, the offsets.h file gets generated before the Rust
target builds.  But, when trying to build just the docs, the dependency
is not explicit, and the file is just not generated.

Fix this by making the dependency explicit.  Like the others, we can't
use the top-level define name, and have to state the dependency target
by expanded name.  This is due to the "fascinating" scoping rules in
cmake.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

CMakeLists.txt

@@ -195,6 +195,7 @@ ${config_paths}
   add_custom_target(librustapp ALL
     DEPENDS ${DUMMY_FILE}
         # The variables, defined at the top level, don't seem to be accessible here.
+        offsets_h
         syscall_list_h_target
         driver_validation_h_target
         kobj_types_h_target
@@ -237,6 +238,7 @@ ${config_paths}
   add_custom_target(rustdoc
     DEPENDS generate_rust_docs
         # The variables, defined at the top level, don't seem to be accessible here.
+        offsets_h
         syscall_list_h_target
         driver_validation_h_target
         kobj_types_h_target