fix: 导入库的条件是对象 ABI,不是 C 库

    -[target.'cfg(all(windows, env = "gnu"))'.build]
    +[target.'cfg(all(windows, not(env = "msvc")))'.build]
     ldflags = ["-lntdll", "-lsynchronization", "-lshell32", "-lkernel32"]

这四个是 Win32 导入库 —— 本包所实现的**平台接口**的性质,不是 C 库的性质。
`env = "gnu"` 一直在代表「GNU/PE 的 ABI 而不是 MSVC 的」,而在传统栈上两者重合。

它们在 C 库改由依赖图供给的那一刻不再重合:一次 `x86_64-windows-gnu` 的
openkal 构建解析出的 C 库是 musl —— mcpp 自己的报告就这么打印:

    kernel-abi  openkal   (openkal-windows@0.1.3, graph)
    c-abi       musl      (openkal-musl@0.3.3, graph)

而拼作 `x86_64-windows-musl` 的是同一次构建的诚实名字。旧谓词下第二个拼法
不带这四个库中的任何一个,实测:

    ld.lld: error: undefined symbol: __declspec(dllimport) GetStdHandle
    ld.lld: error: undefined symbol: __declspec(dllimport) WriteFile
    …

两份 build.ninja 的 ldflags 逐 token 对比,差别只有这四个 token;
连 `--target=x86_64-w64-windows-gnu` 都完全相同 —— 两个 mcpp 三元组翻译成
同一个 LLVM 三元组。

实测(改动后):

    Finished dev in 2.75s
    test3.exe: PE32+ executable (console) x86-64, 14 sections
    imports: ntdll.dll / api-ms-win-core-synch-l1-2-0.dll / SHELL32.dll / KERNEL32.dll
    wine test3.exe → Hello from test3!

`cxxflags = ["-fno-exceptions", "-fno-rtti"]` 在同一张表里,因此一并生效于
两种拼法 —— 那也是对的:它们的理由同样是 ABI 而非 C 库。

⚠️ 兼容性:`x86_64-windows-gnu` 的求值结果不变(`gnu != msvc`),
新增覆盖的是 `msvc` 之外的其它 env 拼法。

related: mcpp-community/mcpp#494

Author: Sunrisepeak

mcpp.toml

@@ -1,7 +1,7 @@
 [package]
 namespace   = "mcpplibs"
 name        = "openkal-windows"
-version     = "0.1.3"
+version     = "0.1.4"
 description = "An implementation of openkal for Windows, written on the Win32 interfaces and the object manager beneath them, using no C runtime symbol."
 license     = "Apache-2.0"
 
@@ -38,7 +38,17 @@ openkal = "0.6.0"
 # the linker and the other as an input file. Naming them once in the spelling of
 # either would make this package build under two of the three toolchains it is
 # written for.
-[target.'cfg(all(windows, env = "gnu"))'.build]
+# ⚠️ THE PREDICATE IS THE OBJECT ABI, NOT THE C LIBRARY.
+#
+# These four are Win32 import libraries — a property of the platform interface
+# this package implements. `env = "gnu"` was standing in for "the GNU/PE ABI
+# rather than the MSVC one", and on a traditional stack the two coincide. They
+# stop coinciding the moment the C library comes from the dependency graph: a
+# build of `x86_64-windows-gnu` over openkal resolves musl, and one spelled
+# `x86_64-windows-musl` is the same build under an honest name. Under the old
+# predicate the second one linked with none of these libraries and failed on
+# `GetStdHandle`.
+[target.'cfg(all(windows, not(env = "msvc")))'.build]
 ldflags = ["-lntdll", "-lsynchronization", "-lshell32", "-lkernel32"]
 
 # Exceptions and run-time type information, on the one ABI where their absence