bpo-30345: Add -g to LDFLAGS for LTO (GH-7709) (GH-7824)

Add -g to LDFLAGS when compiling with LTO to get debug symbols.
(cherry picked from commit 06fe77a)

Co-authored-by: Victor Stinner <vstinner@redhat.com>

Misc/NEWS.d/next/Build/2018-06-15-18-18-16.bpo-30345.j-xRE1.rst

@@ -0,0 +1 @@
+Add -g to LDFLAGS when compiling with LTO to get debug symbols.

configure

@@ -6482,6 +6482,14 @@ if test "$Py_LTO" = 'true' ; then
       esac
       ;;
   esac
+
+  if test "$ac_cv_prog_cc_g" = "yes"
+  then
+      # bpo-30345: Add -g to LDFLAGS when compiling with LTO
+      # to get debug symbols.
+      LTOFLAGS="$LTOFLAGS -g"
+  fi
+
   CFLAGS="$CFLAGS $LTOFLAGS"
   LDFLAGS="$LDFLAGS $LTOFLAGS"
 fi

configure.ac

@@ -1339,6 +1339,14 @@ if test "$Py_LTO" = 'true' ; then
       esac
       ;;
   esac
+
+  if test "$ac_cv_prog_cc_g" = "yes"
+  then
+      # bpo-30345: Add -g to LDFLAGS when compiling with LTO
+      # to get debug symbols.
+      LTOFLAGS="$LTOFLAGS -g"
+  fi
+
   CFLAGS="$CFLAGS $LTOFLAGS"
   LDFLAGS="$LDFLAGS $LTOFLAGS"
 fi