libfabric: properly define HAVE_ALIAS_ATTRIBUTE

@ggouaillardet identified that HAVE_ALIAS_ATTRIBUTE was not properly
being defined in the embedded libfabric.  This is because the
embedded configury missed the test for it (i.e., the real configure.ac
for libfabric always defines HAVE_ALIAS_ATTRIBUTE to 0 or 1 -- we
didn't emulate that properly here in libfabric's configure.m4).

Also, fix some grammar and properly escape another AC_MSG_CHECKING
message in libfabric's configure.m4.

opal/mca/common/libfabric/configure.m4

@@ -205,7 +205,7 @@ AC_DEFUN([_OPAL_COMMON_LIBFABRIC_SETUP_LIBFABRIC_EMBEDDED],[
             # support.
 
             # Check for gcc atomic intrinsics
-            AC_MSG_CHECKING(compiler support for c11 atomics)
+            AC_MSG_CHECKING([if compiler support for c11 atomics])
             AC_TRY_LINK([#include <stdatomic.h>],
                         [atomic_int a;
    atomic_init(&a, 0);
@@ -221,6 +221,21 @@ AC_DEFUN([_OPAL_COMMON_LIBFABRIC_SETUP_LIBFABRIC_EMBEDDED],[
                         ],
                         [AC_MSG_RESULT(no)])
 
+            AC_MSG_CHECKING([if linker supports the alias attribute])
+            AC_LINK_IFELSE(
+                [AC_LANG_SOURCE[
+                        int foo(int arg);
+                        int foo(int arg) { return arg + 3; };
+                        int foo2(int arg) __attribute__ (( __alias__("foo")));
+                        ]],
+                [AC_MSG_RESULT([yes])
+                 opal_common_libfabric_alias_symbols=1],
+                [AC_MSG_RESULT([no])
+                 opal_common_libfabric_alias_symbols=0])
+            AC_DEFINE_UNQUOTED([HAVE_ALIAS_ATTRIBUTE],
+                [$opal_common_libfabric_alias_symbols],
+                [Define to 1 if the linker supports alias attribute.])
+
             # Do stuff for specific providers
             _OPAL_COMMON_LIBFABRIC_EMBEDDED_PROVIDER_USNIC
             _OPAL_COMMON_LIBFABRIC_EMBEDDED_PROVIDER_PSM