Implement isatty

tests/.gitignore

@@ -53,6 +53,7 @@ unistd/fchdir
 unistd/fsync
 unistd/ftruncate
 unistd/getopt
+unistd/isatty
 unistd/pipe
 unistd/rmdir
 unistd/sleep

tests/Makefile

@@ -52,6 +52,7 @@ EXPECT_BINS=\
 	unistd/fsync \
 	unistd/ftruncate \
 	unistd/getopt \
+	unistd/isatty \
 	unistd/pipe \
 	unistd/rmdir \
 	unistd/sleep \

tests/expected/unistd/isatty.stdout

@@ -0,0 +1 @@
+Whatever a tty is, it's not me

tests/unistd/isatty.c

@@ -0,0 +1,11 @@
+#include <stdio.h>
+#include <unistd.h>
+
+int main() {
+    // 1 is stdout
+    if (isatty(1)) {
+        puts("'Tis a tty :D");
+    } else {
+        puts("Whatever a tty is, it's not me");
+    }
+}