Merge #20734: build: Make platform-specific targets available for proper platform builds only

3d31abb build: Make Windows-specific targets available for Windows builds only (Hennadii Stepanov)
92990e2 build: Make macOS-specific targets available for macOS builds only (Hennadii Stepanov)

Pull request description:

  On master (f1dbf92) it is possible to point `make` to macOS and Windows specific targets even the build system is configured to build for Linux platforms:
  ```
  $ make Bitcoin-Core.dmg
  ...
  $ make bitcoin-21.99.0-win64-setup
  ...
  ```

  Such behavior makes no sense, and it is confused. Fixed in this PR.

ACKs for top commit:
  fanquake:
    ACK 3d31abb - tested that nonsensical targets are no longer available. i.e

Tree-SHA512: bbd8450bf98fbccb0b828df2f753ed0dbbd203defa2f58ce21390ee2ea183c95d8ff585d62d52be870dbf0158e2bb0fbd47eda026b80174ee6fd617473f5ac03

Author: fanquake

Makefile.am

@@ -78,6 +78,7 @@ COVERAGE_INFO = $(COV_TOOL_WRAPPER) baseline.info \
 dist-hook:
 	-$(GIT) archive --format=tar HEAD -- src/clientversion.cpp | $(AMTAR) -C $(top_distdir) -xf -
 
+if TARGET_WINDOWS
 $(BITCOIN_WIN_INSTALLER): all-recursive
 	$(MKDIR_P) $(top_builddir)/release
 	STRIPPROG="$(STRIP)" $(INSTALL_STRIP_PROGRAM) $(BITCOIND_BIN) $(top_builddir)/release
@@ -90,6 +91,10 @@ $(BITCOIN_WIN_INSTALLER): all-recursive
 	  echo error: could not build $@
 	@echo built $@
 
+deploy: $(BITCOIN_WIN_INSTALLER)
+endif
+
+if TARGET_DARWIN
 $(OSX_APP)/Contents/PkgInfo:
 	$(MKDIR_P) $(@D)
 	@echo "APPL????" > $@
@@ -133,7 +138,7 @@ $(OSX_BACKGROUND_IMAGE): $(OSX_BACKGROUND_IMAGE).png $(OSX_BACKGROUND_IMAGE)@2x.
 	tiffutil -cathidpicheck $^ -out $@
 
 deploydir: $(OSX_DMG)
-else
+else !BUILD_DARWIN
 APP_DIST_DIR=$(top_builddir)/dist
 APP_DIST_EXTRAS=$(APP_DIST_DIR)/.background/$(OSX_BACKGROUND_IMAGE) $(APP_DIST_DIR)/.DS_Store $(APP_DIST_DIR)/Applications
 
@@ -160,15 +165,11 @@ $(APP_DIST_DIR)/$(OSX_APP)/Contents/MacOS/Bitcoin-Qt: $(OSX_APP_BUILT) $(OSX_PAC
 	INSTALLNAMETOOL=$(INSTALLNAMETOOL) OTOOL=$(OTOOL) STRIP=$(STRIP) $(PYTHON) $(OSX_DEPLOY_SCRIPT) $(OSX_APP) $(OSX_VOLNAME) -translations-dir=$(QT_TRANSLATION_DIR)
 
 deploydir: $(APP_DIST_EXTRAS)
-endif
+endif !BUILD_DARWIN
 
-if TARGET_DARWIN
 appbundle: $(OSX_APP_BUILT)
 deploy: $(OSX_DMG)
 endif
-if TARGET_WINDOWS
-deploy: $(BITCOIN_WIN_INSTALLER)
-endif
 
 $(BITCOIN_QT_BIN): FORCE
 	$(MAKE) -C src qt/$(@F)