util/tests: Avoid int64_t overflow issues in fast_idiv_by_const test

util/tests: Avoid int64_t overflow issues in fast_idiv_by_const test

Flagged by UBSan:

../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:233:14: runtime error: negation of -2147483648 cannot be represented in type 'int'; cast to an unsigned type to negate this value to itself
    #0 0x55b4c1a2a428 in rand_sint ../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:233
    #1 0x55b4c1a2ad3a in random_sdiv_test ../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:308
    #2 0x55b4c1a2b837 in fast_idiv_by_const_int32_Test::TestBody() ../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:410
    #3 0x55b4c1abc13f in void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) ../src/gtest/src/gtest.cc:2402
    #4 0x55b4c1aa7a4d in void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) ../src/gtest/src/gtest.cc:2438
    #5 0x55b4c1a4ce57 in testing::Test::Run() ../src/gtest/src/gtest.cc:2474
    #6 0x55b4c1a4f530 in testing::TestInfo::Run() ../src/gtest/src/gtest.cc:2656
    #7 0x55b4c1a51cbe in testing::TestCase::Run() ../src/gtest/src/gtest.cc:2774
    #8 0x55b4c1a6d698 in testing::internal::UnitTestImpl::RunAllTests() ../src/gtest/src/gtest.cc:4649
    #9 0x55b4c1abfd58 in bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) ../src/gtest/src/gtest.cc:2402
    #10 0x55b4c1aab425 in bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) ../src/gtest/src/gtest.cc:2438
    #11 0x55b4c1a64cba in testing::UnitTest::Run() ../src/gtest/src/gtest.cc:4257
    #12 0x55b4c1ae4b73 in RUN_ALL_TESTS() ../src/gtest/include/gtest/gtest.h:2233
    #13 0x55b4c1ae4a33 in main ../src/gtest/src/gtest_main.cc:37
    #14 0x7ff172d1dbba in __libc_start_main ../csu/libc-start.c:308
    #15 0x55b4c1a28dc9 in _start (/home/daenzer/src/mesa-git/mesa/build-amd64-sanitize/src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test+0x96dc9)

../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:309:52: runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself
    #0 0x563b24dafd2d in random_sdiv_test ../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:309
    #1 0x563b24db0f0f in fast_idiv_by_const_int64_Test::TestBody() ../src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test.cpp:473
    #2 0x563b24e41111 in void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) ../src/gtest/src/gtest.cc:2402
    #3 0x563b24e2ca1f in void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) ../src/gtest/src/gtest.cc:2438
    #4 0x563b24dd1e29 in testing::Test::Run() ../src/gtest/src/gtest.cc:2474
    #5 0x563b24dd4502 in testing::TestInfo::Run() ../src/gtest/src/gtest.cc:2656
    #6 0x563b24dd6c90 in testing::TestCase::Run() ../src/gtest/src/gtest.cc:2774
    #7 0x563b24df266a in testing::internal::UnitTestImpl::RunAllTests() ../src/gtest/src/gtest.cc:4649
    #8 0x563b24e44d2a in bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) ../src/gtest/src/gtest.cc:2402
    #9 0x563b24e303f7 in bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*) ../src/gtest/src/gtest.cc:2438
    #10 0x563b24de9c8c in testing::UnitTest::Run() ../src/gtest/src/gtest.cc:4257
    #11 0x563b24e69b45 in RUN_ALL_TESTS() ../src/gtest/include/gtest/gtest.h:2233
    #12 0x563b24e69a05 in main ../src/gtest/src/gtest_main.cc:37
    #13 0x7f9a90330bba in __libc_start_main ../csu/libc-start.c:308
    #14 0x563b24daddc9 in _start (/home/daenzer/src/mesa-git/mesa/build-amd64-sanitize/src/util/tests/fast_idiv_by_const/fast_idiv_by_const_test+0x96dc9)

v2:
* Use INT64_MIN instead of LLONG_MIN (Jason Ekstrand)
* Simpler test for INT64_MIN result from rand_sint (Jason Ekstrand)

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Adam Jackson <ajax@redhat.com>