all: remove FreeBSD support

FreeBSD support has been broken for a long time, probably since
https://github.com/tinygo-org/tinygo/pull/1860 (merged in May). Nobody
has complained yet, so I am going to assume nobody uses it.

This doesn't remove support for FreeBSD entirely: the code necessary to
build TinyGo on FreeBSD is still there. It just removes the code
necessary to build binaries targetting FreeBSD. But again, it could very
well be broken as we don't test it.

If anybody wants to re-enable support for FreeBSD, they would be welcome
to do that. But I think it would at the very least need a smoke test of
some sort.

compiler/syscall.go

@@ -157,7 +157,7 @@ func (b *builder) createRawSyscall(call *ssa.CallCommon) (llvm.Value, error) {
 // functions, depending on the target OS/arch.
 func (b *builder) createSyscall(call *ssa.CallCommon) (llvm.Value, error) {
 	switch b.GOOS {
-	case "linux", "freebsd":
+	case "linux":
 		syscallResult, err := b.createRawSyscall(call)
 		if err != nil {
 			return syscallResult, err

src/crypto/rand/rand_arc4random.go

@@ -1,4 +1,4 @@
-// +build darwin freebsd tinygo.wasm
+// +build darwin tinygo.wasm
 
 // This implementation of crypto/rand uses the arc4random_buf function
 // (available on both MacOS and WASI) to generate random numbers.

src/os/file_unix.go

@@ -1,4 +1,4 @@
-// +build darwin linux,!baremetal freebsd,!baremetal
+// +build darwin linux,!baremetal
 
 package os
 

src/runtime/os_freebsd.go

@@ -1,5 +0,0 @@
-// +build freebsd
-
-package runtime
-
-const GOOS = "freebsd"

src/runtime/runtime_unix.go

@@ -1,4 +1,4 @@
-// +build darwin linux,!baremetal,!wasi freebsd,!baremetal
+// +build darwin linux,!baremetal,!wasi
 // +build !nintendoswitch
 
 package runtime

src/runtime/runtime_unix_heap.go

@@ -1,4 +1,4 @@
-// +build darwin linux,!baremetal,!wasi freebsd,!baremetal
+// +build darwin linux,!baremetal,!wasi
 // +build !nintendoswitch
 
 // +build gc.conservative gc.leaking

src/runtime/runtime_unix_noheap.go

@@ -1,4 +1,4 @@
-// +build darwin linux,!baremetal,!wasi freebsd,!baremetal
+// +build darwin linux,!baremetal,!wasi
 
 // +build !nintendoswitch