tools: Avoid creating symbolic links for tools/version.h

When building U-Boot host tools for Windows from Microsoft Azure
Pipelines, the following errors were seen:

  HOSTCC  tools/mkenvimage.o
  In file included from tools/mkenvimage.c:25:
  ./tools/version.h:1:1: error: expected identifier or ‘(’ before ‘.’ token
     1 | ../include/version.h
       | ^
  tools/mkenvimage.c: In function ‘main’:
  tools/mkenvimage.c:117:4: warning: implicit declaration of function ‘usage’ [-Wimplicit-function-declaration]
   117 |    usage(prg);
       |    ^~~~~
  tools/mkenvimage.c:120:35: error: ‘PLAIN_VERSION’ undeclared (first use in this function)
   120 |    printf("%s version %s\n", prg, PLAIN_VERSION);
       |                                   ^~~~~~~~~~~~~
  tools/mkenvimage.c:120:35: note: each undeclared identifier is reported only once for each function it appears in
  make[2]: *** [scripts/Makefile.host:114: tools/mkenvimage.o] Error 1

It turns out tools/version.h is a symbolic link and with Windows
default settings it is unsupported hence the actual content of
tools/version.h is not what file include/version.h has, but the
the linked file path, which breaks the build.

To fix this, remove the symbolic links for tools/version.h. Instead
we perform a copy from include/version.h during the build.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>

Makefile

@@ -1837,11 +1837,14 @@ checkarmreloc: u-boot
 		false; \
 	fi
 
-envtools: scripts_basic $(version_h) $(timestamp_h)
+tools/version.h: include/version.h
+	$(call if_changed,copy)
+
+envtools: scripts_basic $(version_h) $(timestamp_h) tools/version.h
 	$(Q)$(MAKE) $(build)=tools/env
 
 tools-only: export TOOLS_ONLY=y
-tools-only: scripts_basic $(version_h) $(timestamp_h)
+tools-only: scripts_basic $(version_h) $(timestamp_h) tools/version.h
 	$(Q)$(MAKE) $(build)=tools
 
 tools-all: export HOST_TOOLS_ALL=y
@@ -1869,7 +1872,7 @@ CLEAN_DIRS  += $(MODVERDIR) \
 	       $(foreach d, spl tpl, $(patsubst %,$d/%, \
 			$(filter-out include, $(shell ls -1 $d 2>/dev/null))))
 
-CLEAN_FILES += include/bmp_logo.h include/bmp_logo_data.h \
+CLEAN_FILES += include/bmp_logo.h include/bmp_logo_data.h tools/version.h \
 	       boot* u-boot* MLO* SPL System.map fit-dtb.blob*
 
 # Directories & files removed with 'make mrproper'

tools/.gitignore

@@ -31,4 +31,5 @@
 /spl_size_limit
 /sunxi-spl-image-builder
 /ubsha1
+/version.h
 /xway-swap-bytes

tools/version.h

@@ -1 +0,0 @@
-../include/version.h