Re: make -C libpq check fails obscurely if tap tests are disabled

I wrote:
> So it'll work in 3.81 (released 2006) and later, but not 3.80.

Confirmed that things are fine with 3.81.

> TBH my inclination here is to move our goalposts to say "we support
> gmake 3.81 and later".

Barring objections, I'll push the attached patch.  I suppose we
could undo whatever dumbing-down was done in _create_recursive_target,
but is it worth troubling with?

            regards, tom lane

diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 32e0d3fd9d..70d188e2bc 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -77,7 +77,7 @@ su - postgres
        <primary>make</primary>
       </indexterm>

-      <acronym>GNU</acronym> <application>make</application> version 3.80 or newer is required; other
+      <acronym>GNU</acronym> <application>make</application> version 3.81 or newer is required; other
       <application>make</application> programs or older <acronym>GNU</acronym> <application>make</application>
versionswill <emphasis>not</emphasis> work. 
       (<acronym>GNU</acronym> <application>make</application> is sometimes installed under
       the name <filename>gmake</filename>.)  To test for <acronym>GNU</acronym>
diff --git a/src/Makefile.global.in b/src/Makefile.global.in
index bb177a8162..0d766cfd15 100644
--- a/src/Makefile.global.in
+++ b/src/Makefile.global.in
@@ -872,11 +872,11 @@ install-strip:
 # allows parallel make across directories and lets make -k and -q work
 # correctly.

-# We need the $(eval) function and order-only prerequisites, which are
-# available in GNU make 3.80.  That also happens to be the version
-# where the .VARIABLES variable was introduced, so this is a simple check.
-ifndef .VARIABLES
-$(error GNU make 3.80 or newer is required.  You are using version $(MAKE_VERSION))
+# We need the ability to export target-specific variables, which was
+# added in GNU make 3.81.  That also happens to be the version
+# where the .FEATURES variable was introduced, so this is a simple check.
+ifndef .FEATURES
+$(error GNU make 3.81 or newer is required.  You are using version $(MAKE_VERSION))
 endif

 # This function is only for internal use below.  It should be called
@@ -884,7 +884,7 @@ endif
 # given subdirectory.  For the tree-wide all/install/check/installcheck cases,
 # ensure we do our one-time tasks before recursing (see targets above).
 # Note that to avoid a nasty bug in make 3.80,
-# this function has to avoid using any complicated constructs (like
+# this function was written to not use any complicated constructs (like
 # multiple targets on a line) and also not contain any lines that expand
 # to more than about 200 bytes.  This is why we make it apply to just one
 # subdirectory at a time, rather than to a list of subdirectories.