build: Error if required module explicitly off

Author: real-or-random

CMakeLists.txt

@@ -67,6 +67,9 @@ if(SECP256K1_ENABLE_MODULE_ELLSWIFT)
 endif()
 
 if(SECP256K1_ENABLE_MODULE_SCHNORRSIG)
+  if(DEFINED SECP256K1_ENABLE_MODULE_EXTRAKEYS AND NOT SECP256K1_ENABLE_MODULE_EXTRAKEYS)
+    message(FATAL_ERROR "schnorrsig module requires explicitly disabled extrakeys module.")
+  endif()
   set(SECP256K1_ENABLE_MODULE_EXTRAKEYS ON)
   add_compile_definitions(ENABLE_MODULE_SCHNORRSIG=1)
 endif()

configure.ac

@@ -393,6 +393,9 @@ if test x"$enable_module_ellswift" = x"yes"; then
 fi
 
 if test x"$enable_module_schnorrsig" = x"yes"; then
+  if test x"$enable_module_extrakeys" = x"no"; then
+    AC_MSG_ERROR("schnorrsig module requires explicitly disabled extrakeys module.")
+  fi
   enable_module_extrakeys=yes
   SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_SCHNORRSIG=1"
 fi