core: define the always-inline attribute macro in one header only

BoxGeometry.hpp and aosoa_pack.hpp carried identical unguarded copies of
ESPRESSO_ATTR_ALWAYS_INLINE; include utils/attributes.hpp instead so the
definition cannot drift between copies.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: RudolfWeeber

src/core/BoxGeometry.hpp

@@ -23,6 +23,7 @@
 #include "lees_edwards/LeesEdwardsBC.hpp"
 
 #include <utils/Vector.hpp>
+#include <utils/attributes.hpp>
 
 #include <bitset>
 #include <cassert>
@@ -31,12 +32,6 @@
 #include <stdexcept>
 #include <utility>
 
-#if defined(__GNUG__) or defined(__clang__)
-#define ESPRESSO_ATTR_ALWAYS_INLINE [[gnu::always_inline]]
-#else
-#define ESPRESSO_ATTR_ALWAYS_INLINE
-#endif
-
 namespace detail {
 /**
  * @brief Get the minimum-image distance between two coordinates.

src/core/aosoa_pack.hpp

@@ -23,6 +23,8 @@
 
 #include "cell_system/CellStructure.hpp"
 
+#include <utils/attributes.hpp>
+
 #include <Kokkos_Core.hpp>
 
 #include <omp.h>
@@ -31,12 +33,6 @@
 #include <cstdint>
 #include <span>
 
-#if defined(__GNUG__) or defined(__clang__)
-#define ESPRESSO_ATTR_ALWAYS_INLINE [[gnu::always_inline]]
-#else
-#define ESPRESSO_ATTR_ALWAYS_INLINE
-#endif
-
 struct CellStructure::AoSoA_pack {
   using PositionViewType =
       Kokkos::View<double *[3], Kokkos::LayoutRight, Kokkos::HostSpace>;

src/utils/include/utils/attributes.hpp

@@ -20,10 +20,7 @@
 #pragma once
 
 /** \file
- *  Compiler-attribute macros shared across utils headers.
- *
- *  Uses the same macro name and guard as the core attributes header, so
- *  either header can be included first without redefinition.
+ *  Compiler-attribute macros shared across ESPResSo headers.
  */
 
 #ifndef ESPRESSO_ATTR_ALWAYS_INLINE