Fix breakages in Linux-only build modes

- compile.com now polyfills -march=native which gcc/clang removed
- Guarantee zero Windows code is linked into non-Windows binaries
- MODE=tinylinux binaries are now back to being as tiny as ~4kb
- Improve the runtime's stack allocation / alignment hack
- GitHub Actions now tests Linux modes for assurance

third_party/lua/lunix.c

@@ -205,7 +205,7 @@ int LuaUnixSysretErrno(lua_State *L, const char *call, int olderr) {
   struct UnixErrno *ep;
   int i, unixerr, winerr;
   unixerr = errno;
-  winerr = GetLastError();
+  winerr = IsWindows() ? GetLastError() : 0;
   if (!IsTiny() && !(0 < unixerr && unixerr < (!IsWindows() ? 4096 : 65536))) {
     WARNF("errno should not be %d", unixerr);
   }

third_party/python/Lib/ntpath.py

@@ -664,10 +664,7 @@ def commonpath(paths):
 try:
     # GetFinalPathNameByHandle is available starting with Windows 6.0.
     # Windows XP and non-Windows OS'es will mock _getfinalpathname.
-    if sys.getwindowsversion()[:2] >= (6, 0):
-        _getfinalpathname = posix._getfinalpathname
-    else:
-        raise ImportError
+    _getfinalpathname = posix._getfinalpathname
 except (AttributeError, ImportError, OSError):
     # On Windows XP and earlier, two files are the same if their absolute
     # pathnames are the same.

third_party/python/Modules/clinic/posixmodule.inc

@@ -946,6 +946,10 @@ os__getfinalpathname(PyObject *module, PyObject *arg)
     PyObject *return_value = NULL;
     PyObject *path;
 
+    if (!IsWindows()) {
+        Py_RETURN_NONE;
+    }
+
     if (!PyArg_Parse(arg, "U:_getfinalpathname", &path)) {
         goto exit;
     }
@@ -1037,6 +1041,9 @@ os__getvolumepathname_impl(PyObject *module, PyObject *path);
 static PyObject *
 os__getvolumepathname(PyObject *module, PyObject **args, Py_ssize_t nargs, PyObject *kwnames)
 {
+    if (!IsWindows()) {
+        Py_RETURN_NONE;
+    }
     PyObject *return_value = NULL;
     static const char * const _keywords[] = {"path", NULL};
     static _PyArg_Parser _parser = {"U:_getvolumepathname", _keywords, 0};

third_party/python/Python/errors.c

@@ -4,6 +4,7 @@
 │ Python 3                                                                     │
 │ https://docs.python.org/3/license.html                                       │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/mem/mem.h"
 #include "libc/nt/enum/formatmessageflags.h"
@@ -11,6 +12,7 @@
 #include "libc/nt/memory.h"
 #include "libc/nt/process.h"
 #include "libc/nt/runtime.h"
+#include "libc/runtime/runtime.h"
 #include "libc/x/x.h"
 #include "third_party/python/Include/abstract.h"
 #include "third_party/python/Include/dictobject.h"
@@ -589,6 +591,10 @@ PyObject *PyErr_SetExcFromWindowsErrWithFilenameObjects(
     PyObject *message;
     PyObject *args, *v;
     uint32_t err = (uint32_t)ierr;
+    if (!IsWindows()) {
+        PyErr_SetString(PyExc_SystemError, "this is not windows");
+        return 0;
+    }
     if (err==0) err = GetLastError();
     len = FormatMessage(
         /* Error API error */

third_party/python/Python/sysmodule.c

@@ -1032,6 +1032,11 @@ sys_getwindowsversion(PyObject *self)
     void *verblock;
     uint32_t verblock_size;
 
+    if (!IsWindows()) {
+        PyErr_SetString(PyExc_SystemError, "this is not windows");
+        return 0;
+    }
+
     ver.dwOSVersionInfoSize = sizeof(ver);
     if (!GetVersionEx(&ver))
         return PyErr_SetFromWindowsErr(0);

third_party/sqlite3/zipfile.c

@@ -1420,8 +1420,8 @@ static int zipfileGetMode(
 ** Both (const char*) arguments point to nul-terminated strings. Argument
 ** nB is the value of strlen(zB). This function returns 0 if the strings are
 ** identical, ignoring any trailing '/' character in either path.  */
-static int zipfileComparePath(const char *zA, const char *zB, int nB){
-  int nA = (int)strlen(zA);
+static int zipfileComparePath(const char *zA, const char *zB, size_t nB){
+  size_t nA = strlen(zA);
   if( nA>0 && zA[nA-1]=='/' ) nA--;
   if( nB>0 && zB[nB-1]=='/' ) nB--;
   if( nA==nB && memcmp(zA, zB, nA)==0 ) return 0;

third_party/xxhash/xxh_x86dispatch.c

@@ -82,10 +82,12 @@ extern "C" {
 #  define XXH_X86DISPATCH_ALLOW_AVX
 #endif
 
+#if 0 /* [jart] be quiet */
 #if defined(__AVX__) && !defined(XXH_X86DISPATCH_ALLOW_AVX)
 #  error "Error: if xxh_x86dispatch.c is compiled with AVX enabled, the resulting binary will crash on sse2-only cpus !! " \
          "If you nonetheless want to do that, please enable the XXH_X86DISPATCH_ALLOW_AVX build variable"
 #endif
+#endif
 
 #ifdef __has_include
 #  define XXH_HAS_INCLUDE(header) __has_include(header)