meson: get version up front

Run the scraper command to establish the project version immediately,
rather than wait for the build to be configured. This simplifies the
code and ensures that project introspection works correctly.

build/meson/meson.build

@@ -23,7 +23,9 @@ project('zstd',
     # so this isn't safe
     #'werror=true'
   ],
-  version: 'DUMMY',
+  version: run_command(
+    find_program('GetZstdLibraryVersion.py'), '../../lib/zstd.h',
+    check: true).stdout().strip(),
   meson_version: '>=0.48.0')
 
 cc = meson.get_compiler('c')
@@ -45,16 +47,6 @@ compiler_msvc = 'msvc'
 
 zstd_version = meson.project_version()
 
-zstd_h_file = join_paths(meson.current_source_dir(), '../../lib/zstd.h')
-GetZstdLibraryVersion_py = find_program('GetZstdLibraryVersion.py', native : true)
-r = run_command(GetZstdLibraryVersion_py, zstd_h_file)
-if r.returncode() == 0
-  zstd_version = r.stdout().strip()
-  message('Project version is now: @0@'.format(zstd_version))
-else
-  error('Cannot find project version in @0@'.format(zstd_h_file))
-endif
-
 zstd_libversion = zstd_version
 
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