try Runfiles API with empty argv0 (as fuzzer doesn't have access to it)

[pk19604014]

bazel run -c opt executable_semantics/fuzzing:executable_semantics_fuzzer
INFO: Invocation ID: 0943c34f-c259-4f18-902c-1ad647c19fdd
INFO: Analyzed target //executable_semantics/fuzzing:executable_semantics_fuzzer (0 packages loaded, 0 targets configured).
INFO: Found 1 target...
Target //executable_semantics/fuzzing:executable_semantics_fuzzer up-to-date:
bazel-bin/executable_semantics/fuzzing/executable_semantics_fuzzer
INFO: Elapsed time: 0.333s, Critical Path: 0.00s
INFO: 1 process: 1 internal.
INFO: Build completed successfully, 1 total action
INFO: Build completed successfully, 1 total action
INFO: found LLVMFuzzerCustomMutator (0x55d01d9f7d70). Disabling -len_control by default.
INFO: Running with entropic power schedule (0xFF, 100).
INFO: Seed: 2531627093
INFO: Loaded 1 modules (15 inline 8-bit counters): 15 [0x55d01dcc6260, 0x55d01dcc626f),
INFO: Loaded 1 PC tables (15 PCs): 15 [0x55d01dcc6270,0x55d01dcc6360),
INFO: -max_len is not provided; libFuzzer will not generate inputs larger than 4096 bytes
current_dir=/usr/local/google/home/pkobyakov/.cache/bazel/_bazel_pkobyakov/0c0c6d5ac7dde4460fd40f446af91e37/execroot/carbon/bazel-out/k8-opt/bin/executable_semantics/fuzzing/executable_semantics_fuzzer.runfiles/carbon
Stack trace:
#0 0x000055d01d97846b backtrace /tmp/llvm-20220302-9880-1faggz0/llvm-project-13.0.1.src/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:4202:13
#1 0x000055d01dbfc183 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/usr/local/google/home/pkobyakov/.cache/bazel/_bazel_pkobyakov/0c0c6d5ac7dde4460fd40f446af91e37/execroot/carbon/bazel-out/k8-opt/bin/executable_semantics/fuzzing/executable_semantics_fuzzer+0x4e1183)
#2 0x000055d01da178cc Carbon::GetRunfilesFile(std::__1::basic_string<char, std::__1::char_traits, std::__1::allocator > const&) (/usr/local/google/home/pkobyakov/.cache/bazel/_bazel_pkobyakov/0c0c6d5ac7dde4460fd40f446af91e37/execroot/carbon/bazel-out/k8-opt/bin/executable_semantics/fuzzing/executable_semantics_fuzzer+0x2fc8cc)
#3 0x000055d01da17f82 Carbon::ParseAndExecute(Carbon::Fuzzing::CompilationUnit const&) (/usr/local/google/home/pkobyakov/.cache/bazel/_bazel_pkobyakov/0c0c6d5ac7dde4460fd40f446af91e37/execroot/carbon/bazel-out/k8-opt/bin/executable_semantics/fuzzing/executable_semantics_fuzzer+0x2fcf82)
#4 0x000055d01d9f833b TestOneProtoInput /proc/self/cwd/executable_semantics/fuzzing/executable_semantics_fuzzer.cpp:10:3
#5 0x000055d01d9f833b LLVMFuzzerTestOneInput /proc/self/cwd/executable_semantics/fuzzing/executable_semantics_fuzzer.cpp:9:1
#6 0x000055d01d8f1334 fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) cxa_noexception.cpp:0:0
#7 0x000055d01d8f2995 fuzzer::Fuzzer::ReadAndExecuteSeedCorpora(std::__Fuzzer::vector<fuzzer::SizedFile, fuzzer::fuzzer_allocatorfuzzer::SizedFile >&) cxa_noexception.cpp:0:0
#8 0x000055d01d8f2e2a fuzzer::Fuzzer::Loop(std::__Fuzzer::vector<fuzzer::SizedFile, fuzzer::fuzzer_allocatorfuzzer::SizedFile >&) cxa_noexception.cpp:0:0
#9 0x000055d01d8e203f fuzzer::FuzzerDriver(int*, char***, int ()(unsigned char const, unsigned long)) cxa_noexception.cpp:0:0
#10 0x000055d01d90c233 main /tmp/llvm-20220302-9880-1faggz0/llvm-project-13.0.1.src/compiler-rt/lib/fuzzer/FuzzerMain.cpp:20:3
#11 0x00007f971edfb7fd __libc_start_main ./csu/../csu/libc-start.c:332:16
#12 0x000055d01d8b8eaa _start (/usr/local/google/home/pkobyakov/.cache/bazel/_bazel_pkobyakov/0c0c6d5ac7dde4460fd40f446af91e37/execroot/carbon/bazel-out/k8-opt/bin/executable_semantics/fuzzing/executable_semantics_fuzzer+0x19deaa)
CHECK failure at executable_semantics/fuzzing/fuzzer_util.cpp:44: runfiles != nullptr