[FYI] {branch-1.13.2} make flags analysis: be more robust

[Stefano Lattarini]

In particular, catering to option-with-argument bundled together
with options-without-arguments, as in:

   # With GNU make 3.82:
   $ make -f- <<<'all:; echo "$$MFLAGS"' -s -k -I none
   -skiI none

   # With development version of GNU make (Git commit b5ea49b):
   $ make -f- <<<'all:; @echo "$$MFLAGS"' -I none
   -skiI none

This fixes some lingering failures in the testsuite; precisely, in
tests 'make-dryrun.tap' and 'make-keepgoing.tap'.

* t/header-vars.am (am__make_running_with_option): Enhance.

Signed-off-by: Stefano Lattarini <address@hidden>
---
 lib/am/header-vars.am | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/lib/am/header-vars.am b/lib/am/header-vars.am
index 64d014c..72a1877 100644
--- a/lib/am/header-vars.am
+++ b/lib/am/header-vars.am
@@ -67,20 +67,26 @@ am__make_running_with_option = \
       esac; \
     fi; \
     am__skip_next=no; \
+    am__strip_trailopt () \
+    { \
+      am__flg=`printf '%s\n' "$$am__flg" | sed "s/$$1.*$$//"`; \
+    }; \
     for am__flg in $$am__flags; do \
       if test $$am__skip_next = yes; then \
         am__skip_next=no; \
         continue; \
       fi; \
       case $$am__flg in \
-        *=*|--*) ;; \
+        *=*|--*) continue;; \
 ## GNU make 3.83 has changed the format of $MFLAGS, and removed the space
 ## between an option and its argument (e.g., from "-I dir" to "-Idir").
 ## So we need to handle both formats.
 ## TODO: we might need to handle similar other cases as well; but let's
-##      wait until the need arises.
-        -I) am__skip_next=yes;; \
-       -I*) continue;; \
+##       wait until the need arises.
+          -*I) am__strip_trailopt 'I'; am__skip_next=yes;; \
+        -*I?*) am__strip_trailopt 'I';; \
+      esac; \
+      case $$am__flg in \
         *$$am__target_option*) am__has_opt=yes; break;; \
       esac; \
     done;\
-- 
1.8.3.rc0.19.g7e6a0cc