Add missing lsan-suppressions.txt to enable ASAN to run with unittests [skip ci]

Change-Id: I007e567af807d2af4d1801a11cd34279d80fd740

cpp/CMakeLists.txt

@@ -291,8 +291,6 @@ include(ThirdpartyToolchain)
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${CXX_COMMON_FLAGS}")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${ARROW_CXXFLAGS}")
 
-message(STATUS "CMAKE_CXX_FLAGS: ${CMAKE_CXX_FLAGS}")
-
 if ("${COMPILER_FAMILY}" STREQUAL "clang")
   # Using Clang with ccache causes a bunch of spurious warnings that are
   # purportedly fixed in the next version of ccache. See the following for details:
@@ -305,7 +303,7 @@ endif()
 
 # ASAN / TSAN / UBSAN
 if(ARROW_FUZZING)
-    set(ARROW_USE_COVERAGE ON)
+  set(ARROW_USE_COVERAGE ON)
 endif()
 include(san-config)
 
@@ -333,6 +331,9 @@ if ("${ARROW_GENERATE_COVERAGE}")
   endif()
 endif()
 
+# CMAKE_CXX_FLAGS now fully assembled
+message(STATUS "CMAKE_CXX_FLAGS: ${CMAKE_CXX_FLAGS}")
+
 # set compile output directory
 string (TOLOWER ${CMAKE_BUILD_TYPE} BUILD_SUBDIR_NAME)
 

cpp/build-support/lsan-suppressions.txt

@@ -0,0 +1,19 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+# False positive from atexit() registration in libc
+leak:*__new_exitfn*