diff --git a/basis/libc/linux/platforms.txt b/basis/libc/linux/platforms.txt
new file mode 100644
index 0000000000..a08e1f35eb
--- /dev/null
+++ b/basis/libc/linux/platforms.txt
@@ -0,0 +1 @@
+linux
diff --git a/basis/libc/macosx/platforms.txt b/basis/libc/macosx/platforms.txt
new file mode 100644
index 0000000000..6e806f449e
--- /dev/null
+++ b/basis/libc/macosx/platforms.txt
@@ -0,0 +1 @@
+macosx
diff --git a/basis/libc/windows/platforms.txt b/basis/libc/windows/platforms.txt
new file mode 100644
index 0000000000..8e1a55995e
--- /dev/null
+++ b/basis/libc/windows/platforms.txt
@@ -0,0 +1 @@
+windows