Use clang-specific linking flags to suppress compact unwind warnings

Update auto-conf submodule

Author: GiudGiud

m4/autoconf-submodule

@@ -227,6 +227,8 @@ AC_DEFUN([LIBMESH_SET_BUILD_FLAGS],
   CFLAGS_DEVEL="$ACSM_CFLAGS_DEVEL"
   CFLAGS_DBG="$ACSM_CFLAGS_DBG"
 
+  LDFLAGS+=" $ACSM_LDFLAGS"
+
   ASSEMBLY_FLAGS="$ACSM_ASSEMBLY_FLAGS"
   NODEPRECATEDFLAG="$ACSM_NODEPRECATEDFLAG"
   OPROFILE_FLAGS="$ACSM_OPROFILE_FLAGS"

m4/compiler.m4

@@ -55,6 +55,7 @@ for method in ${METHODS}; do
      dnl blank line
      AS_ECHO([])
 done
+AS_ECHO(["LDFLAGS............................ : $LDFLAGS"])
 AS_ECHO(["Any warnings-to-errors flags....... : $ACSM_ANY_WERROR_FLAG"])
 AS_ECHO(["Any extra paranoid warning flags... : $ACSM_ANY_PARANOID_FLAGS"])
 AS_ECHO(["Install dir........................ : $prefix"])