cmake: introduce option ENABLE_LIBFUZZER_STATIC_LINKAGE

The patch itnroduces a CMake option ENABLE_LIBFUZZER_STATIC_LINKAGE
that enables static linkage wituh libFuzzer. By default linkage
is disabled.

Needed for google/oss-fuzz#14610

Author: ligurio

CMakeLists.txt

@@ -22,6 +22,7 @@ option(ENABLE_BONUS_TESTS "Enable bonus tests" OFF)
 option(ENABLE_INTERNAL_TESTS "Enable internal tests" OFF)
 option(ENABLE_LAPI_TESTS "Enable Lua API tests" OFF)
 option(ENABLE_CBMC_PROOFS "Enable CBMC proofs" OFF)
+option(ENABLE_LIBFUZZER_STATIC_LINKAGE "Enable static libFuzzer linkage" OFF)
 
 set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake" ${CMAKE_MODULE_PATH})
 set(CMAKE_INCLUDE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake" ${CMAKE_INCLUDE_PATH})
@@ -37,7 +38,7 @@ endif()
 # resulting in drastically slower execution speeds, crash
 # reproduction failures, or inaccurate coverage reports.
 # Disable libFuzzer static linkage when code coverage is enabled.
-if (ENABLE_LAPI_TESTS AND NOT ENABLE_COV)
+if (ENABLE_LAPI_TESTS AND ENABLE_LIBFUZZER_STATIC_LINKAGE AND NOT ENABLE_COV)
   message(STATUS "libFuzzer static linkage is enabled")
   include(LibFuzzer)
   SetLibFuzzerPath(FUZZER_NO_MAIN_LIBRARY)

README.md

@@ -64,6 +64,7 @@ is LuaJIT-specific.
 - `ENABLE_INTERNAL_TESTS` enables internal tests.
 - `ENABLE_LAPI_TESTS` enables Lua API tests.
 - `ENABLE_CBMC_PROOFS` enables building CBMC proofs instead tests.
+- `ENABLE_LIBFUZZER_STATIC_LINKAGE` enables static libFuzzer linkage.
 
 ### Running