configure: add an option to set wrapper CC

This commit adds a new configure option: --with-wrapper-cc. This
option can be used to set which C compiler is invoked by mpicc. The
feature is necessary when building for compiler suites that do not
support C11 (Ex: icc). A version of Open MPI that is set up for these
compilers can be built with:

./configure --with-wrapper-cc=icc CC=gcc FC=ifort CXX=icpc

Signed-off-by: Nathan Hjelm <[email protected]>

Author: hjelmn

config/opal_setup_cc.m4

@@ -38,8 +38,7 @@ AC_DEFUN([OPAL_SETUP_CC],[
 
     # AC_PROG_CC_C99 changes CC (instead of CFLAGS) so save CC (without c99
     # flags) for use in our wrappers.
-    WRAPPER_CC="$CC"
-    AC_SUBST([WRAPPER_CC])
+    # WRAPPER_CC="$CC"
 
     # From Open MPI 1.7 on we require a C99 compiant compiler
     AC_PROG_CC_C99

config/opal_setup_wrappers.m4

@@ -75,6 +75,20 @@ AC_DEFUN([OPAL_WRAPPER_FLAGS_ADD], [
 #     <flag>_prefix, configure is not.  There's no known use case for
 #     doing so, and we'd like to force the issue.
 AC_DEFUN([OPAL_SETUP_WRAPPER_INIT],[
+    AC_ARG_WITH([wrapper-cc],
+                [AC_HELP_STRING([--with-wrapper-cc],
+                                [C compiler to use when using mpicc])])
+
+    AS_IF([test "$with_wrapper_cc" = "yes" || test "$with_wrapper_cc" = "no"],
+          [AC_MSG_ERROR([--with-wrapper-cc must have an argument.])])
+    if test -n "$with_wrapper_cc" ; then
+        WRAPPER_CC="$with_wrapper_cc"
+    else
+        WRAPPER_CC=$(echo "$CC" | cut -d' ' -f1)
+    fi
+
+    AC_SUBST([WRAPPER_CC])
+
     AC_ARG_WITH([wrapper-cflags],
                 [AC_HELP_STRING([--with-wrapper-cflags],
                                 [Extra flags to add to CFLAGS when using mpicc])])