[build, gropdf]: Fix Savannah #63808 (3/3).

* configure.ac: Add Automake conditional, `HAVE_GHOSTSCRIPT`, so that we
  can populate the list of PDF device font tests dynamically.

* font/devpdf/devpdf.am: Test availability of "basic" (PDF base
  14) fonts (plus groff's "EURO") if either Ghostscript or URW fonts are
  available.  Test availability of URW fonts (35) only if Ghostscript
  _and_ the URW fonts were found at configuration time.

Test procedure for Savannah #63808:

./configure --prefix=$HOME
make -j check
make install
make uninstall
test -z "$(find $HOME/{bin,lib,share} -type f)" && echo clean
make distclean

Configurations and test results (total/pass/skip/xfail)
-------------------------------------------------------
without gs, without URW fonts: 161/152/7/2
with gs, without URW fonts: 162/155/5/2
without gs, with URW fonts: 162/153/7/2
with gs, with URW fonts: 163/156/5/2

1 files changed, 12 insertions, 0 deletions

diff --git a/font/devpdf/devpdf.am b/font/devpdf/devpdf.am
index 51e83336e..ff667255e 100644
--- a/font/devpdf/devpdf.am
+++ b/font/devpdf/devpdf.am
@@ -178,12 +178,24 @@ uninstall_devpdf:
 	  rmdir $(DESTDIR)$(devpdffontdir); \
 	fi
 
+# Automake has no logical 'and' operator; we test HAVE_GHOSTSCRIPT and
+# HAVE_URW_FONTS separately, with a potentially redundant assignment.
+
+if HAVE_GHOSTSCRIPT
+font_devpdf_TESTS = \
+  font/devpdf/tests/basic-fonts-present.sh
+endif
+
+if HAVE_URW_FONTS
 font_devpdf_TESTS = \
   font/devpdf/tests/basic-fonts-present.sh
+endif
 
+if HAVE_GHOSTSCRIPT
 if HAVE_URW_FONTS
 font_devpdf_TESTS += font/devpdf/tests/urw-fonts-present.sh
 endif
+endif
 
 TESTS += $(font_devpdf_TESTS)
 EXTRA_DIST += $(font_devpdf_TESTS)