Add IWYU pragmas to private headers which provide library symbols (#1103)

* Add Zephyr build system module.yml (#1074)

The Zephyr build system requires that modules have a `module.yml` file to specify where the module cmake and kconfig files are located. 
These can also be explicitly set as "external" meaning that they do not exist within the module tree, itself. These build file can still be specified elsewhere via cmake variables, explained more in-depth here: https://docs.zephyrproject.org/latest/develop/modules.html#modules-module-ext-root
This change makes it such that ETL can be included more easily in zephyr projects running on embedded systems. A similar change can be observed in the public nanopb repository, where the repo only requires its own `zephyr/module.yml` file to be found by the zephyr build system, but the kconfig and cmake additions can exist outside of the library repository.

* Add full West support for ETL (#1075)

This will allow ETL to be included via west in a zephyr build without any additional wrappers or external kconfigs.

Signed-off-by: Zach Van Camp <[email protected]>
Co-authored-by: Zach Van Camp <[email protected]>

* Add IWYU pragmas to private headers which provide library symbols
This prevents warnings in clang compiler and IWYU tool
https://clangd.llvm.org/guides/include-cleaner#iwyu-pragmas
https://github.com/include-what-you-use/include-what-you-use/blob/master/docs/IWYUPragmas.md#iwyu-pragma-export

---------

Signed-off-by: Zach Van Camp <[email protected]>
Co-authored-by: Zach Van Camp <[email protected]>
Co-authored-by: Zach Van Camp <[email protected]>
Co-authored-by: John Wellbelove <[email protected]>

Author: 4 people

include/etl/bitset.h

@@ -34,9 +34,9 @@ SOFTWARE.
 #include "platform.h"
 
 #if defined(ETL_USE_LEGACY_BITSET)
-  #include "private/bitset_legacy.h"
+  #include "private/bitset_legacy.h" // IWYU pragma: export
 #else
-  #include "private/bitset_new.h"
+  #include "private/bitset_new.h" // IWYU pragma: export
 #endif
 
 #endif

include/etl/delegate.h

@@ -34,9 +34,9 @@ SOFTWARE.
 #include "platform.h"
 
 #if ETL_USING_CPP11 && !defined(ETL_DELEGATE_FORCE_CPP03_IMPLEMENTATION)
-  #include "private/delegate_cpp11.h"
+  #include "private/delegate_cpp11.h" // IWYU pragma: export
 #else
-  #include "private/delegate_cpp03.h"
+  #include "private/delegate_cpp03.h" // IWYU pragma: export
 #endif
 
 #endif

include/etl/variant.h

@@ -34,10 +34,13 @@ SOFTWARE.
 #include "platform.h"
 
 #if ETL_USING_LEGACY_VARIANT
-  #include "private/variant_legacy.h"   // etl::variant
+  // etl::variant
+  #include "private/variant_legacy.h" // IWYU pragma: export
 #else
-  #include "private/variant_legacy.h"   // etl::legacy::variant
-  #include "private/variant_variadic.h" // etl::variant
+  // etl::legacy::variant
+  #include "private/variant_legacy.h" // IWYU pragma: export
+  // etl::variant
+  #include "private/variant_variadic.h" // IWYU pragma: export
 #endif
 
 #endif