Failed to compile with gcc-11 due to gtest.

[xkszltl]

The gtest submodule (1.8) is too old and won't work on gcc-11.

-- Build files have been written to: /tmp/scratch/libgdiplus/gtest_build
make[3]: Entering directory '/tmp/scratch/libgdiplus/gtest_build'
make[4]: Entering directory '/tmp/scratch/libgdiplus/gtest_build'
make[5]: Entering directory '/tmp/scratch/libgdiplus/gtest_build'
make[5]: Leaving directory '/tmp/scratch/libgdiplus/gtest_build'
make[5]: Entering directory '/tmp/scratch/libgdiplus/gtest_build'
[ 12%] Building CXX object googletest/CMakeFiles/gtest.dir/src/gtest-all.cc.o
  CCLD     testregion
  CCLD     testgraphicsdraw
  CCLD     testbmpcodec
In file included from ../../external/googletest/googletest/src/gtest-all.cc:42:
../../external/googletest/googletest/src/gtest-death-test.cc: In function ‘bool testing::internal::StackGrowsDown()’:
../../external/googletest/googletest/src/gtest-death-test.cc:1301:24: error: ‘dummy’ may be used uninitialized [-Werror=maybe-uninitialized]
 1301 |   StackLowerThanAddress(&dummy, &result);
      |   ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
../../external/googletest/googletest/src/gtest-death-test.cc:1290:13: note: by argument 1 of type ‘const void*’ to ‘void testing::internal::StackLowerThanAddress(const void*, bool*)’ declared here
 1290 | static void StackLowerThanAddress(const void* ptr, bool* result) {
      |             ^~~~~~~~~~~~~~~~~~~~~
../../external/googletest/googletest/src/gtest-death-test.cc:1299:7: note: ‘dummy’ declared here
 1299 |   int dummy;
      |       ^~~~~
cc1plus: all warnings being treated as errors
make[5]: *** [googletest/CMakeFiles/gtest.dir/build.make:76: googletest/CMakeFiles/gtest.dir/src/gtest-all.cc.o] Error 1
make[5]: Leaving directory '/tmp/scratch/libgdiplus/gtest_build'
make[4]: *** [CMakeFiles/Makefile2:172: googletest/CMakeFiles/gtest.dir/all] Error 2
make[4]: Leaving directory '/tmp/scratch/libgdiplus/gtest_build'
make[3]: *** [Makefile:146: all] Error 2
make[3]: Leaving directory '/tmp/scratch/libgdiplus/gtest_build'
make[2]: *** [Makefile:1867: ../gtest_build/.stamp-gtest] Error 2
make[2]: Leaving directory '/tmp/scratch/libgdiplus/tests'
make[1]: *** [Makefile:479: all-recursive] Error 1
make[1]: Leaving directory '/tmp/scratch/libgdiplus'
make: *** [Makefile:385: all] Error 2

This is the PR fixing this issue and it's in 1.11.

• Fix warning maybe-uninitialized google/googletest#3024