[lldb][test] Skip beginning/end of file tests on Windows

Added in llvm/llvm-project#137515,
as the source uses unistd.h which isn't present there.

| C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\lldb\test\Shell\Commands/Inputs/sigchld.c:4:10: fatal error: 'unistd.h' file not found
|     4 | #include <unistd.h>
|       |          ^~~~~~~~~~
| 1 error generated.

Author: DavidSpickett

lldb/test/Shell/Commands/command-list-reach-beginning-of-file.test

@@ -1,3 +1,5 @@
+# Source uses unistd.h.
+# UNSUPPORTED: system-windows
 # RUN: %clang_host -g -O0 %S/Inputs/sigchld.c -o %t.out
 # RUN: %lldb %t.out -b -s %s 2>&1 | FileCheck %s
 

lldb/test/Shell/Commands/command-list-reach-end-of-file.test

@@ -1,3 +1,5 @@
+# Source uses unistd.h.
+# UNSUPPORTED: system-windows
 # RUN: %clang_host -g -O0 %S/Inputs/sigchld.c -o %t.out
 # RUN: %lldb %t.out -b -s %s 2>&1 | FileCheck %s
 
@@ -23,4 +25,4 @@ list
 # CHECK: note: Reached end of the file, no more to page
 
 list 
-# CHECK: note: Reached end of the file, no more to page
+# CHECK: note: Reached end of the file, no more to page