liblzma: Enable Intel CET in x86 CRC assembly codes

When Intel CET is enabled, we need to include <cet.h> in assembly codes
to mark Intel CET support and add _CET_ENDBR to indirect jump targets.

Tested on Intel Tiger Lake under CET enabled Linux.

src/liblzma/check/crc32_x86.S

@@ -51,6 +51,14 @@
  * extern uint32_t lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc);
  */
 
+/* When Intel CET is enabled, include <cet.h> in assembly code to mark
+   Intel CET support.  */
+#ifdef __CET__
+# include <cet.h>
+#else
+# define _CET_ENDBR
+#endif
+
 /*
  * On some systems, the functions need to be prefixed. The prefix is
  * usually an underscore.
@@ -83,6 +91,7 @@
 
 	ALIGN(4, 16)
 LZMA_CRC32:
+	_CET_ENDBR
 	/*
 	 * Register usage:
 	 * %eax crc

src/liblzma/check/crc64_x86.S

@@ -41,6 +41,14 @@
  * extern uint64_t lzma_crc64(const uint8_t *buf, size_t size, uint64_t crc);
  */
 
+/* When Intel CET is enabled, include <cet.h> in assembly code to mark
+   Intel CET support.  */
+#ifdef __CET__
+# include <cet.h>
+#else
+# define _CET_ENDBR
+#endif
+
 /*
  * On some systems, the functions need to be prefixed. The prefix is
  * usually an underscore.
@@ -73,6 +81,7 @@
 
 	ALIGN(4, 16)
 LZMA_CRC64:
+	_CET_ENDBR
 	/*
 	 * Register usage:
 	 * %eax crc LSB