Add patch to fix configure script

mandoc-configure_call_make_without_env.patch

@@ -0,0 +1,13 @@
+Index: mandoc-1.14.5/configure
+===================================================================
+--- mandoc-1.14.5.orig/configure
++++ mandoc-1.14.5/configure
+@@ -41,7 +41,7 @@ OSENUM=
+ OSNAME=
+ UTF8_LOCALE=
+ 
+-CC=`printf "all:\\n\\t@echo \\\$(CC)\\n" | env -i make -sf -`
++CC=`printf "all:\\n\\t@echo \\\$(CC)\\n" | make -sf -`
+ CFLAGS=
+ LDADD=
+ LDFLAGS=

mandoc.spec

@@ -14,6 +14,10 @@ Patch1:           mandoc-install-hdr.patch
 # Simplify the compat #if for functions
 Patch2:           mandoc-simplify-compat.patch
 
+# calling with make with an empty env like "env -i | make -sf -"
+# will cause configure to crash
+Patch3:           mandoc-configure_call_make_without_env.patch
+
 BuildRequires:    gcc
 BuildRequires:    make
 BuildRequires:    zlib-devel
@@ -236,6 +240,7 @@ fi
 %changelog
 * Tue Apr 14 2020 Björn Esser <besser82@fedoraproject.org> - 1.14.5-10
 - libmandoc.so must be linked with COMPAT_OBJS
+- Add patch to fix configure script
 
 * Mon Mar 09 2020 David Cantrell - 1.14.5-9
 - BR perl-interpreter