cmake: fix bundled zzip install dir

zzip is installed to lib64/ on some systems by default so we need to
explicitly set the install dir to lib/.

Fixes commit 140fd681 ("cmake: allow to use bundled zzip").

NO_DOC=build
NO_TEST=build
NO_CHANGELOG=build

cmake/BuildZZIP.cmake

@@ -13,6 +13,7 @@ set(ZZIP_CMAKE_FLAGS
     "-DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}"
     "-DCMAKE_C_FLAGS=${ZZIP_CFLAGS}"
     "-DCMAKE_INSTALL_PREFIX=${ZZIP_INSTALL_DIR}"
+    "-DCMAKE_INSTALL_LIBDIR=lib"
     "-DCMAKE_BUILD_TYPE=Release"
     "-DBUILD_STATIC_LIBS=TRUE"
     "-DBUILD_SHARED_LIBS=FALSE"