gnu: make-bootstrap: Allow compilation of the statically-link gawk.

Previously, linking would fail due to the '-fno-common' default in GCC 10:

  ld: /gnu/store/…-glibc-2.33-static/lib/libc.a(getopt.o): in function `_getopt_internal_r':
  (.text+0x6e0): multiple definition of `_getopt_internal_r'; support/libsupport.a(getopt.o):/tmp/guix-build-gawk-5.1.0.drv-0/gawk-5.1.0/support/getopt.c:404: first defined here
  ld: /gnu/store/…-glibc-2.33-static/lib/libc.a(getopt.o): in function `_getopt_internal':

Reported by Thiago Jung Bauermann <bauermann@kolabnow.com>.

* gnu/packages/make-bootstrap.scm (%static-inputs) <gawk>: Remove
getopt.o from libsupport.a.

gnu/packages/make-bootstrap.scm

@@ -206,8 +206,17 @@ for `sh' in $PATH, and without nscd, and with static NSS modules."
                                   (("^xz_LDADD =")
                                    "xz_LDADD = -all-static"))
                                 #t)))))))
-        (gawk (package (inherit gawk)
-                (source (origin (inherit (package-source gawk))
+        (gawk (package
+                (inherit gawk)
+                (source (origin
+                          (inherit (package-source gawk))
+                          (modules '((guix build utils)))
+                          (snippet
+                           ;; Do not build 'getopt.c' since that leads to a
+                           ;; link failure due to duplicate symbols with
+                           ;; 'libc.a'.
+                           '(substitute* "support/Makefile.in"
+                              (("getopt\\.\\$\\(OBJEXT\\)") "")))
                           (patches (cons (search-patch "gawk-shell.patch")
                                          (origin-patches
                                           (package-source gawk))))))