fix(openssl): the xlings sandbox has no os.curdir(), and an unknown call kills install() silently

The diagnostic log added last commit did its job on the first run and contained
exactly one line:

  [mcpp] windows install() start; prefix=D:\a\...\compat-x-openssl\3.5.1

i.e. install() died on the very next statement, os.curdir(), with no message
anywhere — not in the job log, not in xlings' error, which stayed a bare
E_INTERNAL. The xlings sandbox exposes a SUBSET of xmake's Lua API, and calling
outside it terminates the hook silently.

That is a nasty failure mode to debug blind, so it is now structural rather
than a one-off fix: os.curdir() is gone, and every remaining call that might
not be in the sandbox (pkginfo.install_file, os.filedirs, path.absolute,
os.files) goes through a `safe` helper that pcalls it and writes 'call failed:
<name> -> <error>' into the log with a fallback value.

Author: Sunrisepeak

pkgs/c/compat.openssl.lua

@@ -418,9 +418,22 @@ local function _install_windows_impl()
         if fh then fh:write("[mcpp] " .. tostring(msg) .. "\n"); fh:close() end
     end
     note("windows install() start; prefix=" .. tostring(prefix))
-    note("cwd=" .. tostring(os.curdir()))
 
-    local ifile = pkginfo.install_file()
+    -- Every call below goes through this. The xlings sandbox exposes a SUBSET
+    -- of xmake's Lua API, and calling something outside it kills install()
+    -- silently — the first attempt died on os.curdir() with no message at all,
+    -- leaving only the line above in the log. `safe` turns that class of
+    -- failure into a log line naming the call.
+    local function safe(label, fn, fallback)
+        local ok, res = pcall(fn)
+        if not ok then
+            note("call failed: " .. label .. " -> " .. tostring(res))
+            return fallback
+        end
+        return res
+    end
+
+    local ifile = safe("pkginfo.install_file()", function() return pkginfo.install_file() end)
     note("install_file=" .. tostring(ifile))
     local srcroot = ifile and tostring(ifile):replace(".tar.gz", "")
                             or ("openssl-" .. pkginfo.version())
@@ -429,12 +442,13 @@ local function _install_windows_impl()
         srcroot = "openssl-" .. pkginfo.version()
     end
     if not os.isdir(srcroot) then
-        note("FATAL: no source dir found; entries in cwd:")
-        for _, f in ipairs(os.filedirs("*")) do note("   " .. tostring(f)) end
+        note("FATAL: no source dir found. Entries beside it:")
+        local entries = safe("os.filedirs('*')", function() return os.filedirs("*") end, {})
+        for _, f in ipairs(entries) do note("   " .. tostring(f)) end
         return false
     end
-    srcroot = path.absolute(srcroot)
-    note("srcroot=" .. srcroot)
+    srcroot = safe("path.absolute(srcroot)", function() return path.absolute(srcroot) end, srcroot)
+    note("srcroot=" .. tostring(srcroot))
 
     -- vswhere is installed with every VS 2017+ at a fixed location, and is the
     -- supported way to find the toolset; hardcoding a VS path breaks on the
@@ -480,7 +494,8 @@ local function _install_windows_impl()
     local libdir = path.join(prefix, "lib")
     note("checking " .. libdir)
     if os.isdir(libdir) then
-        for _, f in ipairs(os.files(path.join(libdir, "*"))) do note("   lib/ " .. tostring(f)) end
+        local produced = safe("os.files(lib/*)", function() return os.files(path.join(libdir, "*")) end, {})
+        for _, f in ipairs(produced) do note("   lib/ " .. tostring(f)) end
     else
         note("   (no lib/ directory was produced)")
     end