configure.ac: Not all pkg-config support PKG_CHECK_MODULES_STATIC

PKG_CHECK_MODULES_STATIC is only supported by pkg-config > 0.29

Use pkg-config --static instead.

configure.ac

@@ -520,12 +520,15 @@ if test "x$build_dtls" = "xyes"; then
  # Attempt to find MbedTLS using pkg-config.
 
  # When statically linking against libcoap, all transitive dependencies need to be specified as linker flags
- # as well. Use PKG_CHECK_MODULES_STATIC for that.
+ # as well. Use pkg-config --static for that.
  if test "x$enable_static" = "xyes"; then
- PKG_CHECK_MODULES_STATIC([MbedTLS],
- [mbedtls],
- [have_mbedtls="yes"; mbedtls_has_pkgconfig="yes"],
- [have_mbedtls="no"; mbedtls_has_pkgconfig="no"])
+ KEEP_PKG_CONFIG=$PKG_CONFIG
+ PKG_CONFIG="$PKG_CONFIG --static"
+ PKG_CHECK_MODULES([MbedTLS],
+ [mbedtls],
+ [have_mbedtls="yes"; mbedtls_has_pkgconfig="yes"],
+ [have_mbedtls="no"; mbedtls_has_pkgconfig="no"])
+ PKG_CONFIG=$KEEP_PKG_CONFIG
  else
  PKG_CHECK_MODULES([MbedTLS],
  [mbedtls],