Include 'libfuzzer_exports.h' in fuzzers that are missing it

This is part of a workaround in the Chromium build infrastructure for
the fact that on Mac, the linker tends to strip LLVMFuzzer*
implementation because of how they are loaded/used.

All of the rest of the machinary is already setup and working, just
need to actually include the header. Dawn and other fuzzers use this
same fix.

BUG=chromium:1319605

Change-Id: Ifced8e0b29a48cdf64cd82002c90eb3c765b01c0
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/98880
Auto-Submit: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>

src/tint/fuzzers/fuzzer_init.cc

@@ -12,8 +12,11 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "src/tint/fuzzers/fuzzer_init.h"
+#include <cstddef>
+
 #include "src/tint/fuzzers/cli.h"
+#include "src/tint/fuzzers/fuzzer_init.h"
+#include "testing/libfuzzer/libfuzzer_exports.h"
 
 namespace tint::fuzzers {
 

src/tint/fuzzers/tint_ast_fuzzer/fuzzer.cc

@@ -21,9 +21,9 @@
 #include "src/tint/fuzzers/tint_ast_fuzzer/override_cli_params.h"
 #include "src/tint/fuzzers/tint_common_fuzzer.h"
 #include "src/tint/fuzzers/transform_builder.h"
-
 #include "src/tint/reader/wgsl/parser.h"
 #include "src/tint/writer/wgsl/generator.h"
+#include "testing/libfuzzer/libfuzzer_exports.h"
 
 namespace tint::fuzzers::ast_fuzzer {
 namespace {

src/tint/fuzzers/tint_regex_fuzzer/fuzzer.cc

@@ -24,6 +24,7 @@
 #include "src/tint/fuzzers/transform_builder.h"
 #include "src/tint/reader/wgsl/parser.h"
 #include "src/tint/writer/wgsl/generator.h"
+#include "testing/libfuzzer/libfuzzer_exports.h"
 
 namespace tint::fuzzers::regex_fuzzer {
 namespace {

src/tint/fuzzers/tint_spirv_tools_fuzzer/fuzzer.cc

@@ -27,6 +27,7 @@
 #include "src/tint/fuzzers/tint_spirv_tools_fuzzer/spirv_opt_mutator.h"
 #include "src/tint/fuzzers/tint_spirv_tools_fuzzer/spirv_reduce_mutator.h"
 #include "src/tint/fuzzers/tint_spirv_tools_fuzzer/util.h"
+#include "testing/libfuzzer/libfuzzer_exports.h"
 
 namespace tint::fuzzers::spvtools_fuzzer {
 namespace {