Disable C plugins on Cygwin

configure.ac

@@ -96,6 +96,9 @@ else
 fi
 
 # c
+if test "x$PLATFORM" = xcygwin; then
+    AM_CONDITIONAL([BUILD_C_API], [false])
+else
     LT_INIT
     if test "x$enable_plugins" = xno; then
         AM_CONDITIONAL([BUILD_C_API], [false])
@@ -110,6 +113,7 @@ elif test "x$enable_c_plugins" != xno; then
     else
         AM_CONDITIONAL([BUILD_C_API], [false])
     fi
+fi
 
 # threading
 ACX_PTHREAD([], [AC_MSG_ERROR([pthread is required])])