[master] ee0939bf0 build: Retire zlib-specific flags

[Dridi Boukelmoune]

commit ee0939bf032fb9d5977a1e142a2fcaa2faa8078d
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Mon Jun 26 17:32:46 2023 +0200

    build: Retire zlib-specific flags
    
    But retain the ability to specify them:
    
        make VGZ_CFLAGS=-Wfoo
    
    We may need them again if new warnings crop up when we sync with zlib in
    the future, or if we retire libvgz in favor of a vanilla zlib.
    
    Refs 3df9cdc1eda72ec736c603b818387fb8ab825569

diff --git a/configure.ac b/configure.ac
index c1877cee0..7a6af4796 100644
--- a/configure.ac
+++ b/configure.ac
@@ -695,13 +695,6 @@ if test $? -ne 0 ; then
 fi
 
 # zlib-specific flags
-AX_CHECK_COMPILE_FLAG([-Wno-error=strict-prototypes],
-	[VGZ_CFLAGS="$VGZ_CFLAGS -Wno-error=strict-prototypes"])
-
-dnl https://github.com/madler/zlib/issues/633
-AX_CHECK_COMPILE_FLAG([-Wno-error=deprecated-non-prototype],
-	[VGZ_CFLAGS="$VGZ_CFLAGS -Wno-error=deprecated-non-prototype"])
-
 AC_SUBST(VGZ_CFLAGS)
 
 # Support for visibility attribute (zlib)