unwind: restore the LINKER_LANGUAGE

Have CMake treat the unwind libraries as C libraries rather than C++.
There is no C++ runtime dependency at runtime.  This ensures that we do
not accidentally end up with a link against the C++ runtime.

We need to explicitly reset the implicitly linked libraries for C++ to
ensure that we do not have CMake force the link against the C++ runtime.
This adjustment should enable the NetBSD bots to be happy with this
change.

Author: compnerd

libunwind/src/CMakeLists.txt

@@ -108,6 +108,10 @@ set_property(SOURCE ${LIBUNWIND_CXX_SOURCES}
 set_property(SOURCE ${LIBUNWIND_C_SOURCES}
              APPEND_STRING PROPERTY COMPILE_FLAGS " ${LIBUNWIND_C_FLAGS}")
 
+# NOTE: avoid implicit dependencies on C++ runtimes.  libunwind uses C++ for
+# ease, but does not rely on C++ at runtime.
+set(CMAKE_CXX_IMPLICIT_LINK_LIBRARIES "")
+
 # Build the shared library.
 if (LIBUNWIND_ENABLE_SHARED)
   add_library(unwind_shared SHARED ${LIBUNWIND_SOURCES} ${LIBUNWIND_HEADERS})
@@ -126,6 +130,7 @@ if (LIBUNWIND_ENABLE_SHARED)
     CXX_STANDARD_REQUIRED ON
     COMPILE_FLAGS "${LIBUNWIND_COMPILE_FLAGS}"
     LINK_FLAGS "${LIBUNWIND_LINK_FLAGS}"
+    LINKER_LANGUAGE C
     OUTPUT_NAME "unwind"
     VERSION "1.0"
     SOVERSION "1")
@@ -150,6 +155,7 @@ if (LIBUNWIND_ENABLE_STATIC)
     CXX_STANDARD_REQUIRED ON
     COMPILE_FLAGS "${LIBUNWIND_COMPILE_FLAGS}"
     LINK_FLAGS "${LIBUNWIND_LINK_FLAGS}"
+    LINKER_LANGUAGE C
     OUTPUT_NAME "unwind")
 
   if(LIBUNWIND_HERMETIC_STATIC_LIBRARY)