Add GWP-ASan fuzz target to compiler-rt/tools.

Summary:
@eugenis to approve addition of //compiler-rt/tools.
@pree-jackie please confirm that this WFY.

D66494 introduced the GWP-ASan stack_trace_compressor_fuzzer. Building fuzz
targets in compiler-rt is a new affair, and has some challenges:
- If the host compiler doesn't have compiler-rt, the -fsanitize=fuzzer may not
  be able to link against `libclang_rt.fuzzer*`.
- Things in compiler-rt generally aren't built when you want to build with
  sanitizers using `-DLLVM_USE_SANITIZER`. This tricky to work around, so
  we create the new tools directory so that we can build fuzz targets with
  sanitizers. This has the added bonus of fixing the problem above as well, as
  we can now just guard the fuzz target build to only be done with
  `-DLLVM_USE_SANITIZE_COVERAGE=On`.

Reviewers: eugenis, pree-jackie

Reviewed By: eugenis, pree-jackie

Subscribers: dberris, mgorny, #sanitizers, llvm-commits, eugenis, pree-jackie, lebedev.ri, vitalybuka, morehouse

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D66776

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@370094 91177308-0d34-0410-b5e6-96231b3b80d8

Author: hctim

Diff for: CMakeLists.txt

@@ -513,3 +513,5 @@ if(COMPILER_RT_INCLUDE_TESTS)
     endif()
   endif()
 endif()
+
+add_subdirectory(tools)

Diff for: lib/gwp_asan/CMakeLists.txt

@@ -98,29 +98,6 @@ if (COMPILER_RT_HAS_GWP_ASAN)
       SOURCES optional/backtrace_sanitizer_common.cpp
       ADDITIONAL_HEADERS ${GWP_ASAN_BACKTRACE_HEADERS}
       CFLAGS ${GWP_ASAN_CFLAGS} ${SANITIZER_COMMON_CFLAGS})
-
-  # Build the stack trace compressor fuzzer. Note that clang versions 4.* did
-  # not have -fsanitize=fuzzer, and Clang versions 5.* didn't have
-  # -fsanitize=fuzzer-no-link. In general, the way we build fuzz targets in LLVM
-  # core is to link it against a dummy main when DLLVM_USE_SANITIZE_COVERAGE
-  # isn't specified. Instead, here we only build fuzz targets if clang version
-  # is >= 6.0.
-  if (COMPILER_RT_BUILD_LIBFUZZER AND
-      "${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" AND
-      NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 6.0)
-    add_executable(stack_trace_compressor_fuzzer
-        stack_trace_compressor_fuzzer.cpp
-        ${GWP_ASAN_SOURCES}
-        ${GWP_ASAN_HEADERS})
-    set_target_properties(
-        stack_trace_compressor_fuzzer PROPERTIES FOLDER "Fuzzers")
-    target_compile_options(
-        stack_trace_compressor_fuzzer PRIVATE -fsanitize=fuzzer-no-link)
-    set_target_properties(
-        stack_trace_compressor_fuzzer PROPERTIES LINK_FLAGS -fsanitize=fuzzer)
-    add_dependencies(stack_trace_compressor_fuzzer fuzzer)
-    add_dependencies(gwp_asan stack_trace_compressor_fuzzer)
-  endif()
 endif()
 
 if(COMPILER_RT_INCLUDE_TESTS)

Diff for: tools/CMakeLists.txt

@@ -0,0 +1 @@
+add_subdirectory(gwp_asan)

Diff for: tools/gwp_asan/CMakeLists.txt

@@ -0,0 +1,20 @@
+# Build the stack trace compressor fuzzer. This will require Clang >= 6.0.0, as
+# -fsanitize=fuzzer-no-link was not a valid command line flag prior to this.
+if (LLVM_USE_SANITIZE_COVERAGE)
+  add_executable(stack_trace_compressor_fuzzer
+      ../../lib/gwp_asan/stack_trace_compressor.cpp
+      ../../lib/gwp_asan/stack_trace_compressor.h
+      stack_trace_compressor_fuzzer.cpp)
+  set_target_properties(
+      stack_trace_compressor_fuzzer PROPERTIES FOLDER "Fuzzers")
+  target_compile_options(
+      stack_trace_compressor_fuzzer PRIVATE -fsanitize=fuzzer-no-link)
+  set_target_properties(
+      stack_trace_compressor_fuzzer PROPERTIES LINK_FLAGS -fsanitize=fuzzer)
+  target_include_directories(
+      stack_trace_compressor_fuzzer PRIVATE ../../lib/)
+
+  if (TARGET gwp_asan)
+    add_dependencies(gwp_asan stack_trace_compressor_fuzzer)
+  endif()
+endif()