failed to generate due to missing of "limits.h"

log of llcppg:

2025/03/21 15:31:51 llcppg: cannot generate: 
go: creating new go.mod: module gmp
go: added github.com/goplus/llgo v0.10.0
2025/03/21 15:31:51 File "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/limits.h" not found in FileMap. Available files:
/Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/sys/_posix_availability.h
/Library/Developer/CommandLineTools/usr/lib/clang/14.0.3/include/stddef.h
/Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/i386/_limits.h
/Library/Developer/CommandLineTools/usr/lib/clang/14.0.3/include/__stddef_max_align_t.h
/Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/limits.h
/Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/i386/limits.h
/Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/sys/syslimits.h
/Library/Developer/CommandLineTools/usr/lib/clang/14.0.3/include/limits.h
/Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/sys/cdefs.h
/Users/qiniu/.conan2/p/b/gmp0639b84a0b2df/p/include/gmp.h
/Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/sys/_symbol_aliasing.h
/Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/machine/limits.h
panic: File "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/limits.h" not found in FileMap. Available files:
        /Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/sys/_posix_availability.h
        /Library/Developer/CommandLineTools/usr/lib/clang/14.0.3/include/stddef.h
        /Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/i386/_limits.h
        /Library/Developer/CommandLineTools/usr/lib/clang/14.0.3/include/__stddef_max_align_t.h
        /Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/limits.h
        /Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/i386/limits.h
        /Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/sys/syslimits.h
        /Library/Developer/CommandLineTools/usr/lib/clang/14.0.3/include/limits.h
        /Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/sys/cdefs.h
        /Users/qiniu/.conan2/p/b/gmp0639b84a0b2df/p/include/gmp.h
        /Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/sys/_symbol_aliasing.h
        /Library/Developer/CommandLineTools/SDKs/MacOSX13.sdk/usr/include/machine/limits.h

goroutine 1 [running]:
log.Panicf({0x2a9b2dd?, 0x3b9?}, {0xc00003db90?, 0x2b0f5f0?, 0x1?})
        /Users/qiniu/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.23.7.darwin-amd64/src/log/log.go:439 +0x65
github.com/goplus/llcppg/cmd/gogensig/convert.(*Converter).setCurFile(0xc0002e40d8, {0xc00002a6e0, 0x48})
        /Users/qiniu/llcppg/cmd/gogensig/convert/convert.go:154 +0x28d
github.com/goplus/llcppg/cmd/gogensig/convert.(*Converter).Process.func1({0xc00002a6e0?, 0xc00003ddd8?}, 0x2a766f8?, {0x2a891c2, 0x5}, 0xc00003dd88)
        /Users/qiniu/llcppg/cmd/gogensig/convert/convert.go:87 +0x71
github.com/goplus/llcppg/cmd/gogensig/convert.(*Converter).Process(0xc0002e40d8)
        /Users/qiniu/llcppg/cmd/gogensig/convert/convert.go:94 +0xf4
github.com/goplus/llcppg/cmd/gogensig/convert.(*Converter).Convert(0xc0002e40d8)
        /Users/qiniu/llcppg/cmd/gogensig/convert/convert.go:74 +0x18
main.main()
        /Users/qiniu/llcppg/cmd/gogensig/gogensig.go:80 +0x4f4
panic: exit status 2

goroutine 1 [running]:
main.check(...)
        /Users/qiniu/llcppg/llcppg.go:190
main.do({0x7ff7bc0545ff, 0xa}, 0x3, 0x0)
        /Users/qiniu/llcppg/llcppg.go:184 +0x34c
main.main()
        /Users/qiniu/llcppg/llcppg.go:158 +0x37c

Reproduce the llcppg generation failure on macOS, then start with setCurFile in cmd/gogensig/convert/convert.go and the callers in gogensig.go and llcppg.go. Trace how SDK header paths enter the FileMap and verify generation against the reported MacOSX and MacOSX13 paths. Done means the missing limits.h case is handled without a panic and generation completes.