Makefile: remove accidental recipe prefix in conditional

Back in 728b9ac (Makefile(s): avoid recipe prefix in conditional
statements, 2024-04-08), we prepared our Makefiles for a forthcoming
change in upstream Make that would ban the recipe prefix within a
conditional statement by replacing tabs (the prefix) with eight spaces.

In b9d6f64 (compat/zlib: allow use of zlib-ng as backend,
2025-01-28), a handful of recipe prefix characters were introduced in a
conditional statement ('ifdef ZLIB_NG'), causing 'make' to fail on my
system, which uses GNU Make 4.4.90.

Remove the recipe prefix characters by replacing them with the same
script as is mentioned in 728b9ac.

Signed-off-by: Taylor Blau <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: ttaylorr

Makefile

@@ -1690,16 +1690,16 @@ IMAP_SEND_LDFLAGS += $(OPENSSL_LINK) $(OPENSSL_LIBSSL) $(LIB_4_CRYPTO)
 
 ifdef ZLIB_NG
 	BASIC_CFLAGS += -DHAVE_ZLIB_NG
-	ifdef ZLIB_NG_PATH
+        ifdef ZLIB_NG_PATH
 		BASIC_CFLAGS += -I$(ZLIB_NG_PATH)/include
 		EXTLIBS += $(call libpath_template,$(ZLIB_NG_PATH)/$(lib))
-	endif
+        endif
 	EXTLIBS += -lz-ng
 else
-	ifdef ZLIB_PATH
+        ifdef ZLIB_PATH
 		BASIC_CFLAGS += -I$(ZLIB_PATH)/include
 		EXTLIBS += $(call libpath_template,$(ZLIB_PATH)/$(lib))
-	endif
+        endif
 	EXTLIBS += -lz
 endif