build: update toolchains_llvm dependency

WORKSPACE.bazel

@@ -48,10 +48,11 @@ filegroup(
 )
 
 http_archive(
-    name = "com_grail_bazel_toolchain",
-    sha256 = "da607faed78c4cb5a5637ef74a36fdd2286f85ca5192222c4664efec2d529bb8",
-    strip_prefix = "bazel-toolchain-0.6.3",
-    urls = ["https://github.com/grailbio/bazel-toolchain/archive/refs/tags/0.6.3.tar.gz"],
+    name = "toolchains_llvm",
+    canonical_id = "0.10.3",
+    sha256 = "b7cd301ef7b0ece28d20d3e778697a5e3b81828393150bed04838c0c52963a01",
+    strip_prefix = "toolchains_llvm-0.10.3",
+    url = "https://github.com/bazel-contrib/toolchains_llvm/releases/download/0.10.3/toolchains_llvm-0.10.3.tar.gz",
 )
 
 http_archive(
@@ -154,20 +155,24 @@ load("@contrib_rules_jvm//:setup.bzl", "contrib_rules_jvm_setup")
 
 contrib_rules_jvm_setup()
 
-load("@com_grail_bazel_toolchain//toolchain:deps.bzl", "bazel_toolchain_dependencies")
+load("@toolchains_llvm//toolchain:deps.bzl", "bazel_toolchain_dependencies")
 
 bazel_toolchain_dependencies()
 
-load("@com_grail_bazel_toolchain//toolchain:rules.bzl", "llvm_toolchain")
+load("@toolchains_llvm//toolchain:rules.bzl", "llvm_toolchain")
 
 llvm_toolchain(
     name = "llvm_toolchain",
-    llvm_version = "13.0.0",
+    llvm_version = "15.0.6",
     sysroot = {
         "linux-x86_64": "@org_chromium_sysroot_linux_x64//:sysroot",
     },
 )
 
+load("@llvm_toolchain//:toolchains.bzl", "llvm_register_toolchains")
+
+llvm_register_toolchains()
+
 load("@rules_jvm_external//:repositories.bzl", "rules_jvm_external_deps")
 
 rules_jvm_external_deps()

tests/BUILD.bazel

@@ -530,7 +530,7 @@ java_fuzz_target_test(
         "--instrumentation_includes=com.example.**",
         "--custom_hook_includes=com.example.**",
         # Limit runs to catch regressions in mutator efficiency and speed up test runs.
-        "-runs=1200000",
+        "-runs=1500000",
     ],
     target_class = "com.example.ExperimentalMutatorComplexProtoFuzzer",
     verify_crash_reproducer = False,