configure: Clarify that `--with-gmp-libraries` has not effect for bindists

libraries/ghc-bignum/GMP.rst

@@ -47,7 +47,7 @@ GMP is linked:
 
   --with-gmp                     enable GMP backend
   --with-gmp-includes            directory containing gmp.h
-  --with-gmp-libraries           directory containing gmp library
+  --with-gmp-libraries           directory containing gmp library; ineffective for bindists
   --with-intree-gmp              force using the in-tree GMP
   --with-gmp-framework-preferred on OSX, prefer the GMP framework to the gmp lib
 

libraries/ghc-bignum/configure.ac

@@ -25,7 +25,7 @@ AC_ARG_WITH([gmp-includes],
 
 AC_ARG_WITH([gmp-libraries],
   [AS_HELP_STRING([--with-gmp-libraries],
-    [directory containing gmp library])],
+    [directory containing gmp library; ineffective for bindists])],
     [GMP_LIB_DIRS=$withval; LDFLAGS="-L$withval"],
     [GMP_LIB_DIRS=])
 

m4/fp_gmp.m4

@@ -13,7 +13,7 @@ AC_DEFUN([FP_GMP],
 
   AC_ARG_WITH([gmp-libraries],
     [AS_HELP_STRING([--with-gmp-libraries],
-      [directory containing gmp library])],
+      [directory containing gmp library; ineffective for bindists])],
       [GMP_LIB_DIRS=$withval])
 
   AC_ARG_WITH([intree-gmp],