build: Do not link s-s-d against libihash and libshouldbeinlibc on GNU/Hurd

These libraries are not used now, and the linking is unnecessary and
superfluous.

The libps interfaces used to expose or required the caller to use
functions from those other libraries long time ago, not anymore though.

debian/changelog

@@ -66,6 +66,8 @@ dpkg (1.17.7) UNRELEASED; urgency=low
       their usage depending on system macros.
     - Add a new --ppid matching option to check for parent PID.
       Suggested by Alex Mestiashvili <mailatgoogl@gmail.com>.
+    - On GNU/Hurd do not link unnecessarily against libshouldbeinlibc and
+      libihash.
 
   [ Updated dpkg translations ]
   * German (Sven Joachim).

m4/dpkg-libs.m4

@@ -134,8 +134,6 @@ fi
 # Check for start-stop-daemon libraries.
 AC_DEFUN([DPKG_LIB_SSD],
 [AC_ARG_VAR([SSD_LIBS], [linker flags for start-stop-daemon])dnl
-AC_CHECK_LIB([ihash], [ihash_create], [SSD_LIBS="${SSD_LIBS:+$SSD_LIBS }-lihash"])
 AC_CHECK_LIB([ps], [proc_stat_list_create], [SSD_LIBS="${SSD_LIBS:+$SSD_LIBS }-lps"])
-AC_CHECK_LIB([shouldbeinlibc], [fmt_past_time], [SSD_LIBS="${SSD_LIBS:+$SSD_LIBS }-lshouldbeinlibc"])
 AC_CHECK_LIB([kvm], [kvm_openfiles], [SSD_LIBS="${SSD_LIBS:+$SSD_LIBS }-lkvm"])
 ])# DPKG_LIB_SSD