Fix linking with pthreads on CMake (#5194)

.gitignore

@@ -46,3 +46,6 @@ verilator-config-version.cmake
 /test_regress/snapshot/
 xmverilog.*
 xrun.history
+
+# Normal CMake build directory
+/build

CMakeLists.txt

@@ -30,6 +30,7 @@ include(GNUInstallDirs)
 include(CMakePackageConfigHelpers)
 include(CheckStructHasMember)
 include(ExternalProject)
+include(FindThreads)
 
 if (NOT WIN32)
     message(WARNING "CMake support on Linux/OSX is experimental.")

src/CMakeLists.txt

@@ -488,6 +488,8 @@ add_dependencies(${verilator}
     V3PreLex_yy_cpp${CMAKE_BUILD_TYPE}
 )
 
+target_link_libraries(${verilator} PRIVATE Threads::Threads)
+
 # verilated_cov_key.h is only regenerated in a single-configuration environment.
 # This limitation can be lifted when `add_dependencies` will support generator
 # expressions. See https://gitlab.kitware.com/cmake/cmake/issues/19467