Fix WASIX build

WASIX is missing a couple common functions like fchdir() and ctermid().
Add some configure-time checks for those.

Link: wasix-org/wasix-libc#105

Author: tavianator

build/has/ctermid.c

@@ -0,0 +1,9 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+#include <stdio.h>
+
+int main(void) {
+	char path[L_ctermid];
+	return !ctermid(path);
+}

build/has/fchdir.c

@@ -0,0 +1,8 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+#include <unistd.h>
+
+int main(void) {
+	return fchdir(0);
+}

build/header.mk

@@ -22,11 +22,13 @@ HEADERS := \
     gen/has/acl-trivial.h \
     gen/has/builtin-riscv-pause.h \
     gen/has/confstr.h \
+    gen/has/ctermid.h \
     gen/has/dprintf.h \
     gen/has/extattr-get-file.h \
     gen/has/extattr-get-link.h \
     gen/has/extattr-list-file.h \
     gen/has/extattr-list-link.h \
+    gen/has/fchdir.h \
     gen/has/fdclosedir.h \
     gen/has/getdents.h \
     gen/has/getdents64-syscall.h \

src/bfstd.c

@@ -645,11 +645,15 @@ pid_t xwaitpid(pid_t pid, int *status, int flags) {
 }
 
 int open_cterm(int flags) {
+#if BFS_HAS_CTERMID
 	char path[L_ctermid];
 	if (ctermid(path) == NULL || strlen(path) == 0) {
 		errno = ENOTTY;
 		return -1;
 	}
+#else
+	const char *path = "/dev/tty";
+#endif
 
 	return open(path, flags);
 }
@@ -1019,7 +1023,7 @@ size_t xstrwidth(const char *str) {
 	mbstate_t mb = {0};
 	while (i < len) {
 		wint_t wc = xmbrtowc(str, &i, len, &mb);
-		if (wc == WEOF) {
+		if (wc == (wint_t)WEOF) {
 			// Assume a single-width '?'
 			++ret;
 			continue;
@@ -1103,7 +1107,7 @@ static size_t printable_len(const char *str, size_t len, enum wesc_flags flags)
 	mbstate_t mb = {0};
 	for (size_t j = i; i < len; i = j) {
 		wint_t wc = xmbrtowc(str, &j, len, &mb);
-		if (wc == WEOF) {
+		if (wc == (wint_t)WEOF) {
 			break;
 		}
 		if (!wesc_iswprint(wc, flags)) {
@@ -1153,7 +1157,7 @@ static char *dollar_quote(char *dest, char *end, const char *str, size_t len, en
 		bool safe = false;
 
 		wint_t wc = xmbrtowc(str, &i, len, &mb);
-		if (wc != WEOF) {
+		if (wc != (wint_t)WEOF) {
 			safe = wesc_iswprint(wc, flags);
 		}
 

src/eval.c

@@ -1187,7 +1187,7 @@ static void eval_status(struct bfs_eval *state, struct bfs_bar *bar, size_t coun
 	for (size_t i = lhslen; lhslen < pathlen; lhslen = i) {
 		wint_t wc = xmbrtowc(status, &i, pathlen, &mb);
 		int cwidth;
-		if (wc == WEOF) {
+		if (wc == (wint_t)WEOF) {
 			// Invalid byte sequence, assume a single-width '?'
 			cwidth = 1;
 		} else {

src/xspawn.c

@@ -238,6 +238,7 @@ int bfs_spawn_adddup2(struct bfs_spawn *ctx, int oldfd, int newfd) {
 #define BFS_POSIX_SPAWN_AFTER_FCHDIR !__NetBSD__
 
 int bfs_spawn_addfchdir(struct bfs_spawn *ctx, int fd) {
+#if BFS_HAS_FCHDIR
 	struct bfs_spawn_action *action = bfs_spawn_action(BFS_SPAWN_FCHDIR);
 	if (!action) {
 		return -1;
@@ -275,6 +276,10 @@ int bfs_spawn_addfchdir(struct bfs_spawn *ctx, int fd) {
 	action->in_fd = fd;
 	SLIST_APPEND(ctx, action);
 	return 0;
+#else // !BFS_HAS_FCHDIR
+	errno = ENOTSUP;
+	return -1;
+#endif
 }
 
 int bfs_spawn_setrlimit(struct bfs_spawn *ctx, int resource, const struct rlimit *rl) {
@@ -627,10 +632,15 @@ static void bfs_spawn_exec(struct bfs_resolver *res, const struct bfs_spawn *ctx
 			}
 			break;
 		case BFS_SPAWN_FCHDIR:
+#if BFS_HAS_FCHDIR
 			if (fchdir(action->in_fd) != 0) {
 				goto fail;
 			}
 			break;
+#else
+			errno = ENOTSUP;
+			goto fail;
+#endif
 		case BFS_SPAWN_SETRLIMIT:
 			if (setrlimit(action->resource, &action->rlimit) != 0) {
 				goto fail;