tools/ci/platforms/darwin.sh: update bloaty pin

This seems to fix build errors on my environment.
(macOS 15.1.1, x86-64, xcode 16.1)

```
/Users/yamamoto/git/nuttx/tools/bloaty-src/third_party/abseil-cpp/absl/numeric/int128.cc:45:5: error: use of undeclared identifier 'ABSL_INTERNAL_ASSUME'
   45 |     ABSL_INTERNAL_ASSUME(hi != 0);
      |     ^
/Users/yamamoto/git/nuttx/tools/bloaty-src/third_party/abseil-cpp/absl/numeric/int128.cc:49:3: error: use of undeclared identifier 'ABSL_INTERNAL_ASSUME'
   49 |   ABSL_INTERNAL_ASSUME(low != 0);
      |   ^
/Users/yamamoto/git/nuttx/tools/bloaty-src/third_party/abseil-cpp/absl/numeric/int128.cc:141:9: error: redefinition of 'operator/'
  141 | uint128 operator/(uint128 lhs, uint128 rhs) {
      |         ^
/usr/local/Cellar/abseil/20240722.0/include/absl/numeric/int128.h:1040:16: note: previous definition is here
 1040 | inline uint128 operator/(uint128 lhs, uint128 rhs) {
      |                ^
/Users/yamamoto/git/nuttx/tools/bloaty-src/third_party/abseil-cpp/absl/numeric/int128.cc:152:9: error: redefinition of 'operator%'
  152 | uint128 operator%(uint128 lhs, uint128 rhs) {
      |         ^
```

tools/ci/platforms/darwin.sh

@@ -130,7 +130,8 @@ bloaty() {
     cd "${NUTTXTOOLS}"/bloaty-src
     # Due to issues with latest MacOS versions use pinned commit.
     # https://github.com/google/bloaty/pull/326
-    git checkout 52948c107c8f81045e7f9223ec02706b19cfa882
+    # https://github.com/google/bloaty/pull/347
+    git checkout 6b78e080efcb63fa4ef9d2c1f062e3d5bf158e94
     mkdir -p "${NUTTXTOOLS}"/bloaty
     cmake -B build/bloaty -GNinja -D BLOATY_PREFER_SYSTEM_CAPSTONE=NO -D CMAKE_INSTALL_PREFIX="${NUTTXTOOLS}"/bloaty
     cmake --build build/bloaty