Fix macOS build: make Windows-only libraries conditional

- DevIL, bundled zlib, and xcompress64 only linked on Windows
- macOS/Linux use system zlib (-lz)
- DLL deployment only on Windows

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/app.pro

@@ -23,15 +23,25 @@ FORMS                   += $$files($$PWD/*.ui)
 
 RESOURCES               += ../data/Data.qrc
 
+# Core libraries (all platforms)
 LIBS                    += \
-                        -L$$PWD/../third_party/devil_sdk/lib/ -lDevIL -lILU -lILUT \
-                        -L$$PWD/../third_party/zlib/lib/ -lzlib \
-                        -L$$PWD/../third_party/xbox_sdk/lib -lxcompress64 \
                         -L$$OUT_PWD/../libs/ -lcore \
                         -L$$OUT_PWD/../libs/ -lcompression \
                         -L$$OUT_PWD/../libs/ -ldsl \
                         -L$$OUT_PWD/../libs/ -lencryption
 
+# Windows-only: DevIL, bundled zlib, Xbox SDK
+win32 {
+    LIBS += -L$$PWD/../third_party/devil_sdk/lib/ -lDevIL -lILU -lILUT
+    LIBS += -L$$PWD/../third_party/zlib/lib/ -lzlib
+    LIBS += -L$$PWD/../third_party/xbox_sdk/lib -lxcompress64
+}
+
+# macOS/Linux: use system zlib
+unix {
+    LIBS += -lz
+}
+
 INCLUDEPATH             += \
                         $$PWD/../third_party/devil_sdk/include/ \
                         $$PWD/../third_party/zlib/include \
@@ -62,7 +72,11 @@ defs_install.files     = $$PWD/../definitions/*
 scripts_install.path = $$FULL_OUT_DIR/scripts
 scripts_install.files  = $$PWD/../scripts/*
 
-dll_install.path = $$FULL_OUT_DIR
-dll_install.files  = $$PWD/../third_party/xbox_sdk/lib/xcompress64.dll
+INSTALLS              += defs_install scripts_install
 
-INSTALLS              += defs_install scripts_install dll_install
+# Windows-only: deploy DLLs
+win32 {
+    dll_install.path = $$FULL_OUT_DIR
+    dll_install.files  = $$PWD/../third_party/xbox_sdk/lib/xcompress64.dll
+    INSTALLS += dll_install
+}

tools/cli/cli.pro

@@ -13,7 +13,11 @@ SOURCES += main.cpp
 
 # Link against the DSL library
 LIBS += -L$$OUT_PWD/../../libs -ldsl -lcompression -lcore -lencryption
-LIBS += -L$$PWD/../../third_party/xbox_sdk/lib -lxcompress64
+
+# Windows-only: Xbox SDK
+win32 {
+    LIBS += -L$$PWD/../../third_party/xbox_sdk/lib -lxcompress64
+}
 
 # Include paths
 INCLUDEPATH += \
@@ -32,7 +36,9 @@ CONFIG(debug, debug|release) {
     FULL_OUT_DIR = $$OUT_PWD/release
 }
 
-dll_install.path = $$FULL_OUT_DIR
-dll_install.files  = $$PWD/../../third_party/xbox_sdk/lib/xcompress64.dll
-
-INSTALLS              += dll_install
+# Windows-only: deploy DLLs
+win32 {
+    dll_install.path = $$FULL_OUT_DIR
+    dll_install.files  = $$PWD/../../third_party/xbox_sdk/lib/xcompress64.dll
+    INSTALLS += dll_install
+}