[lmi] Check bashisms in makefiles

[Greg Chicares]

Vadim, do you know of a better tool to check for bashisms in makefiles
than 'checkbashisms'? Here's what that script says:

--------8<--------8<--------8<--------8<--------8<--------
$checkbashisms --extra --force --posix *make* 2>&1 |sed -e'/does not appear to 
have a #! interpreter line/d' -e'/^you may get strange results$/d'
possible bashism in install_mingw.make line 108 (type):
        type "$(WGET)" >/dev/null || { $(ECHO) -e $(wget_missing)   && false; }
possible bashism in workhorse.make line 983 (echo -n):
fardel_date_script := \
  d0=`$(DATE) +%Y-%m-01`; \
  d1=`$(DATE) --utc --date="$$d0 + 1 month " +%s`; \
  d2=`$(DATE) --utc --date="$$d0 + 2 months" +%s`; \
  j1=`expr 2440588 + $$d1 / 86400`; \
  j2=`expr 2440588 + $$d2 / 86400`; \
  echo -n "$$j1 $$j2" >expiry; \

possible bashism in workhorse.make line 1317 ('$(< foo)' should be '$(cat 
foo)'):
        @$(DIFF) --brief $(system_test_md5sums) $(touchstone_md5sums) \
          && $(ECHO) "All `<$(touchstone_md5sums) $(WC) -l` files match." \
          || $(MAKE) --file=$(this_makefile) system_test_discrepancies
-------->8-------->8-------->8-------->8-------->8--------

The last one (line 1317) is a false positive: there, $(foo) is a 'make'
variable representing the name of a file we redirect from. The others
are valid, but the list is incomplete--I know that because when I tried
  $make release_candidate
I saw this, where the last quoted line has an unwanted literal "-e":

$git diff
diff --git a/version.hpp b/version.hpp
index cb53c48..2cf5edb 100644
--- a/version.hpp
+++ b/version.hpp
@@ -1,4 +1,4 @@
-// Copyright (C) 2016 Gregory W. Chicares.
+-e  // Copyright (C) 2016 Gregory W. Chicares.

Of course, 'dash' has exposed a latent error here:
  release_candidate:
          @$(ECHO) -e \
            $(gpl_notices) \
and it would be best to fix bashisms or zshisms all at once, if only I
had a tool that could detect them all.