pw_bluetooth_sapphire: Handle C99 warning with pigweed

Handle C99 extensions warning with pigweed diagnostics.

Bug: b/355511476
Test: fx test //src/connectivity/bluetooth/core/bt-host

Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1092957
GitOrigin-RevId: e0381227753aff4229124822910e9d0e2c765188
Change-Id: Ie65a53c84c33c9fcfbc2632db728c0f0fd3d5c1c
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/230552
Commit-Queue: Jason Graffius <[email protected]>
Reviewed-by: Lulu Wang <[email protected]>
Lint: Lint 🤖 <[email protected]>

pw_bluetooth_sapphire/host/common/byte_buffer_test.cc

@@ -19,11 +19,10 @@
 #include <cstddef>
 #include <type_traits>
 
+#include "pw_bluetooth_sapphire/internal/host/common/macros.h"
 #include "pw_bluetooth_sapphire/internal/host/testing/test_helpers.h"
 #include "pw_unit_test/framework.h"
 
-#pragma clang diagnostic ignored "-Wc99-extensions"
-
 namespace bt {
 namespace {
 
@@ -518,13 +517,16 @@ TEST(ByteBufferTest, ByteBufferToDoesNotReadUnaligned) {
 }
 
 TEST(ByteBufferTest, ByteBufferReadMember) {
+  PW_MODIFY_DIAGNOSTICS_PUSH();
+  PW_MODIFY_DIAGNOSTIC_CLANG(ignored, "-Wc99-extensions");
   struct [[gnu::packed]] Point {
     uint8_t x;
     const uint8_t y;
     const uint8_t array[2];
     char multi[2][1];
     uint8_t flex[];
   };
+  PW_MODIFY_DIAGNOSTICS_POP();
 
   StaticByteBuffer data(0x01, 0x02, 0x03, 0x37, 0x7f, 0x02, 0x45);
   auto x = data.ReadMember<&Point::x>();
@@ -608,10 +610,13 @@ TEST(ByteBufferDeathTest, ByteBufferReadMemberOfStdArrayType) {
 }
 
 TEST(ByteBufferDeathTest, ByteBufferReadMemberOfFlexibleArrayType) {
+  PW_MODIFY_DIAGNOSTICS_PUSH();
+  PW_MODIFY_DIAGNOSTIC_CLANG(ignored, "-Wc99-extensions");
   struct [[gnu::packed]] Point {
     uint16_t dimensions;
     int8_t coordinates[];
   };
+  PW_MODIFY_DIAGNOSTICS_POP();
 
   StaticByteBuffer data(0, 0, 0x01, 0x02);
   ASSERT_LE(sizeof(Point), data.size());