Highlighted erros from mkmf.log
find_library: checking for pthread_create() in -lpthread... -------------------- yes
"x86_64-w64-mingw32-gcc -o conftest.exe -IC:/Ruby25-x64/include/ruby-2.5.0/x64-mingw32 -IC:/Ruby25-x64/include/ruby-2.5.0/ruby/backward -IC:/Ruby25-x64/include/ruby-2.5.0 -I. -IC:/Ruby25-x64/msys64/mingw64/include -IC:/qlite3 -IC:/sqlite3/include -D_FORTIFY_SOURCE=2 -D__USE_MINGW_ANSI_STDIO=1 -DFD_SETSIZE=2048 -D_WIN32_WINNT=0x0501 -D__MINGW_USE_VC2005_COMPAT -D_FILE_OFFSET_BITS=64 -march=x86-64 -mtune=generic -O2 -pipe conftest.c -L. -LC:/Ruby25-x64/lib -LC:/qlite3 -LC:/sqlite3/lib -L. -pipe -s -LC:/Ruby25-x64/msys64/mingw64/lib -lsqlite3 -lx64-msvcrt-ruby250 -lpthread -lsqlite3 -lgmp -lshell32 -lws2_32 -liphlpapi -limagehlp -lshlwapi "
conftest.c: In function 't':
conftest.c:16:57: error: 'pthread_create' undeclared (first use in this function); did you mean 'rb_thread_create'?
int t(void) { void ((*volatile p)()); p = (void ((*)()))pthread_create; return !p; }
^~~~~~~~~~~~~~
rb_thread_create
--------------------
have_library: checking for -ldl... -------------------- no
"x86_64-w64-mingw32-gcc -o conftest.exe -IC:/Ruby25-x64/include/ruby-2.5.0/x64-mingw32 -IC:/Ruby25-x64/include/ruby-2.5.0/ruby/backward -IC:/Ruby25-x64/include/ruby-2.5.0 -I. -IC:/Ruby25-x64/msys64/mingw64/include -IC:/qlite3 -IC:/sqlite3/include -D_FORTIFY_SOURCE=2 -D__USE_MINGW_ANSI_STDIO=1 -DFD_SETSIZE=2048 -D_WIN32_WINNT=0x0501 -D__MINGW_USE_VC2005_COMPAT -D_FILE_OFFSET_BITS=64 -march=x86-64 -mtune=generic -O2 -pipe conftest.c -L. -LC:/Ruby25-x64/lib -LC:/qlite3 -LC:/sqlite3/lib -L. -pipe -s -LC:/Ruby25-x64/msys64/mingw64/lib -lpthread -lsqlite3 -lx64-msvcrt-ruby250 -ldl -lpthread -lsqlite3 -lgmp -lshell32 -lws2_32 -liphlpapi -limagehlp -lshlwapi "
C:/Ruby25-x64/msys64/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/8.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: cannot find -ldl
collect2.exe: error: ld returned 1 exit status
have_func: checking for dlopen()... -------------------- no
"x86_64-w64-mingw32-gcc -o conftest.exe -IC:/Ruby25-x64/include/ruby-2.5.0/x64-mingw32 -IC:/Ruby25-x64/include/ruby-2.5.0/ruby/backward -IC:/Ruby25-x64/include/ruby-2.5.0 -I. -IC:/Ruby25-x64/msys64/mingw64/include -IC:/qlite3 -IC:/sqlite3/include -D_FORTIFY_SOURCE=2 -D__USE_MINGW_ANSI_STDIO=1 -DFD_SETSIZE=2048 -D_WIN32_WINNT=0x0501 -D__MINGW_USE_VC2005_COMPAT -D_FILE_OFFSET_BITS=64 -march=x86-64 -mtune=generic -O2 -pipe conftest.c -L. -LC:/Ruby25-x64/lib -LC:/qlite3 -LC:/sqlite3/lib -L. -pipe -s -LC:/Ruby25-x64/msys64/mingw64/lib -lpthread -lsqlite3 -lx64-msvcrt-ruby250 -lpthread -lsqlite3 -lgmp -lshell32 -lws2_32 -liphlpapi -limagehlp -lshlwapi "
conftest.c: In function 't':
conftest.c:16:57: error: 'dlopen' undeclared (first use in this function); did you mean '_lopen'?
int t(void) { void ((*volatile p)()); p = (void ((*)()))dlopen; return !p; }
^~~~~~
_lopen
conftest.c:16:57: note: each undeclared identifier is reported only once for each function it appears in