[PATCH bpf-next] libbpf: hashmap.h update to fix build issues using LLVM14

[Eduard Zingerman <eddyz87@gmail.com>]

A fix for the LLVM compilation error while building bpftool.
Replaces the expression:

  _Static_assert((p) == NULL || ...)

by expression:

  _Static_assert((__builtin_constant_p((p)) ? (p) == NULL : 0) || ...)

When "p" is not a constant the former is not considered to be a
constant expression by LLVM 14.

The error was introduced in the following patch-set: [1].
The error was reported here: [2].

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>

[1] https://lore.kernel.org/bpf/20221109142611.879983-1-eddyz87@gmail.com/
[2] https://lore.kernel.org/all/202211110355.BcGcbZxP-lkp@intel.com/
---
 tools/lib/bpf/hashmap.h   | 3 ++-
 tools/perf/util/hashmap.h | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/hashmap.h b/tools/lib/bpf/hashmap.h
index 3fe647477bad..0a5bf1937a7c 100644
--- a/tools/lib/bpf/hashmap.h
+++ b/tools/lib/bpf/hashmap.h
@@ -123,7 +123,8 @@ enum hashmap_insert_strategy {
 };
 
 #define hashmap_cast_ptr(p) ({								\
-	_Static_assert((p) == NULL || sizeof(*(p)) == sizeof(long),			\
+	_Static_assert((__builtin_constant_p((p)) ? (p) == NULL : 0) ||			\
+				sizeof(*(p)) == sizeof(long),				\
 		       #p " pointee should be a long-sized integer or a pointer");	\
 	(long *)(p);									\
 })
diff --git a/tools/perf/util/hashmap.h b/tools/perf/util/hashmap.h
index 3fe647477bad..0a5bf1937a7c 100644
--- a/tools/perf/util/hashmap.h
+++ b/tools/perf/util/hashmap.h
@@ -123,7 +123,8 @@ enum hashmap_insert_strategy {
 };
 
 #define hashmap_cast_ptr(p) ({								\
-	_Static_assert((p) == NULL || sizeof(*(p)) == sizeof(long),			\
+	_Static_assert((__builtin_constant_p((p)) ? (p) == NULL : 0) ||			\
+				sizeof(*(p)) == sizeof(long),				\
 		       #p " pointee should be a long-sized integer or a pointer");	\
 	(long *)(p);									\
 })
-- 
2.34.1