Merge remote-tracking branch 'upstream/pr/1171' * upstream/pr/1171: ci: install pkg-config in mingw-w64 CI build: test ac_cv_header_sys_time_h once, reformat timer* macro checks build: remove call to AC_C_CONST() build: replace ntp_pkg_config macro with a call to PKG_PROG_PKG_CONFIG() build: remove NTP_PKG_CONFIG call from libevent_mbedtls.m4 build: stop using the deprecated form of AC_OUTPUT() build: quote args in AC_ARG_ENABLE & AS_HELP_STRING build: remove call to AC_HEADER_TIME build: call AC_PREREQ() first & quote argument build: remove call to AC_PREFIX_DEFAULT build: remove call to AC_PROG_GCC_TRADITIONAL