package/libcpprestsdk: zlib is optional, not mandatory

The CMakeLists.txt contains:

  if(CPPREST_EXCLUDE_COMPRESSION)
  if(NOT CPPREST_EXCLUDE_BROTLI)
  message(FATAL_ERROR "Use of Brotli requires compression to be enabled")
  endif()

libcpprestsdk requires openssl, so if the libopenssl provider is
chosen, it anyway pulls in zlib. But if libressl is used as a
provider, it doesn't pull in zlib, and building libcpprestsdk becomes
possible without zlib thanks to this patch.

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/libcpprestsdk/Config.in

@@ -14,7 +14,6 @@ config BR2_PACKAGE_LIBCPPRESTSDK
 	select BR2_PACKAGE_BOOST_REGEX
 	select BR2_PACKAGE_BOOST_THREAD
 	select BR2_PACKAGE_OPENSSL
-	select BR2_PACKAGE_ZLIB
 	help
 	  The C++ REST SDK is a Microsoft project for cloud-based
 	  client-server communication in native code using a modern

package/libcpprestsdk/libcpprestsdk.mk

@@ -10,7 +10,7 @@ LIBCPPRESTSDK_LICENSE = MIT
 LIBCPPRESTSDK_LICENSE_FILES = license.txt
 LIBCPPRESTSDK_SUBDIR = Release
 LIBCPPRESTSDK_INSTALL_STAGING = YES
-LIBCPPRESTSDK_DEPENDENCIES += host-pkgconf boost openssl zlib
+LIBCPPRESTSDK_DEPENDENCIES += host-pkgconf boost openssl
 LIBCPPRESTSDK_CONF_OPTS = -DWERROR=OFF -DBUILD_SAMPLES=OFF
 
 ifeq ($(BR2_STATIC_LIBS),y)
@@ -25,12 +25,19 @@ ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
 LIBCPPRESTSDK_CXXFLAGS += -latomic
 endif
 
+ifeq ($(BR2_PACKAGE_ZLIB),y)
+LIBCPPRESTSDK_DEPENDENCIES += zlib
+LIBCPPRESTSDK_CONF_OPTS += -DCPPREST_EXCLUDE_COMPRESSION=OFF
+# brotli needs compression
 ifeq ($(BR2_PACKAGE_BROTLI),y)
 LIBCPPRESTSDK_DEPENDENCIES += brotli
 LIBCPPRESTSDK_CONF_OPTS += -DCPPREST_EXCLUDE_BROTLI=OFF
 else
 LIBCPPRESTSDK_CONF_OPTS += -DCPPREST_EXCLUDE_BROTLI=ON
 endif
+else
+LIBCPPRESTSDK_CONF_OPTS += -DCPPREST_EXCLUDE_COMPRESSION=ON
+endif
 
 ifeq ($(BR2_PACKAGE_WEBSOCKETPP),y)
 LIBCPPRESTSDK_DEPENDENCIES += websocketpp