[Warnings] Removed -lz Flag from Compilation

The -lz flag is used to link with the ZLIB library, but the library was
already being linked; so there was no reason to add the flag. This was
causing an insane number of warnings in the Clang build. If this is
added back for any reason, this should be checked.

Also cleaned up how ZLIB was being linked. ZLIB is required for reading
and processing the atom circuit; so it should always be linked with VPR.

CMakeLists.txt

@@ -130,11 +130,6 @@ endif()
 # Build type flags
 #
 
-set(EXTRA_FLAGS "")
-if(VPR_ENABLE_INTERCHANGE)
-    set(EXTRA_FLAGS "-lz")
-endif()
-
 if(NOT MSVC)
     # for GCC and Clang
     set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -O0 -g3")
@@ -298,6 +293,7 @@ endif()
 #
 # Increased debugging vebosity
 #
+set(EXTRA_FLAGS "")
 if(VTR_ENABLE_VERBOSE)
     set(EXTRA_FLAGS "${EXTRA_FLAGS} -DVTR_ENABLE_DEBUG_LOGGING")
     message(STATUS "Enabling increased debugging verbosity")

vpr/CMakeLists.txt

@@ -109,21 +109,22 @@ endif ()
 set_target_properties(libvpr PROPERTIES PREFIX "") #Avoid extra 'lib' prefix
 
 #Specify link-time dependencies
+find_package(ZLIB)
 target_link_libraries(libvpr
-                        libvtrutil
-                        libarchfpga
-                        libsdcparse
-                        libblifparse
-                        libtatum
-                        libargparse
-                        libpugixml
-                        librrgraph
+                      libvtrutil
+                      libarchfpga
+                      libsdcparse
+                      libblifparse
+                      libtatum
+                      libargparse
+                      libpugixml
+                      librrgraph
+                      ZLIB::ZLIB
 )
 
 if(VPR_USE_SERVER)
     target_link_libraries(libvpr
                           sockpp-static
-                          -lz
     )
 endif()