Merge #2971: [Build] Check for libgmp directly

18b7faa [Build] Check for libgmp directly (Fuzzbawls)

Pull request description:

  Refactors the libgmp check during configure to use pkgconfig if available, and fallback to using autoconf's check header/check lib.

  Removes the m4 script as these checks can just be done directly in configure.ac.

ACKs for top commit: 18b7faa
  Duddino:
    ACK 18b7faa
  Liquid369:
    ACK 18b7faa

Tree-SHA512: 89fb95dcb94768bfb44e45e6dc57e92572a300d5dfe30a79a44871ba5f7605320df9f3f0a2eda5ca456ffdb5e90756ea1495de57e7d97a0484e2c3a4d5bfb157

Author: Fuzzbawls

build-aux/m4/gmp.m4

@@ -1169,6 +1169,7 @@ if test x$use_pkgconfig = xyes; then
           PKG_CHECK_MODULES([EVENT_PTHREADS], [libevent_pthreads], [], [AC_MSG_ERROR([libevent_pthreads not found.])])
         fi
         PKG_CHECK_MODULES([SODIUM], [libsodium], [], [AC_MSG_ERROR([libsodium not found.])])
+        PKG_CHECK_MODULES([GMP], [gmp], [], [AC_MSG_ERROR([libgmp not found.])])
       fi
 
       if test "x$use_zmq" = "xyes"; then
@@ -1192,6 +1193,8 @@ else
     fi
     AC_CHECK_HEADER([sodium/core.h], [], [AC_MSG_ERROR([libsodium headers missing])])
     AC_CHECK_LIB([sodium], [main], [SODIUM_LIBS=-lsodium], [AC_MSG_ERROR([libsodium missing])])
+    AC_CHECK_HEADER([gmp.h], [], [AC_MSG_ERROR([libgmp headers missing])])
+    AC_CHECK_LIB([gmp], [__gmpz_init], [LIBS="$LIBS -lgmp"], [AC_MSG_ERROR([libgmp missing])])
   fi
 
   if test "x$use_zmq" = "xyes"; then
@@ -1225,12 +1228,6 @@ else
   fi
 fi
 
-dnl gmp check
-GMP_CHECK
-if test x"$has_gmp" != x"yes"; then
-  AC_MSG_ERROR([libgmp not found])
-fi
-
 dnl univalue check
 
 need_bundled_univalue=yes