liblzma: Fix building with NVHPC (NVIDIA HPC SDK).

NVHPC compiler has several issues that make it impossible to
build liblzma:
  - the compiler cannot handle unions that contain pointers that
    are not the first members;
  - the compiler fails to produce valid code for delta_decode if the
    vectorization is enabled, which results in failed tests.

This introduces NVHPC-specific workarounds that address the issues.

(This commit was contributed under 0BSD but the author confirmed
that it is fine to backport it to the public domain branches. See
https://github.com/tukaani-project/xz/pull/90#issuecomment-2100185936
and the next two messages.)

(cherry picked from commit 096bc0e3f8)

src/liblzma/common/string_conversion.c

@@ -218,12 +218,14 @@ typedef struct {
 	uint16_t offset;
 
 	union {
+// NVHPC has problems with unions that contain pointers that are not the first
+// members
+		const name_value_map *map;
+
 		struct {
 			uint32_t min;
 			uint32_t max;
 		} range;
-
-		const name_value_map *map;
 	} u;
 } option_map;
 

src/liblzma/delta/delta_decoder.c

@@ -26,6 +26,9 @@ decode_buffer(lzma_delta_coder *coder, uint8_t *buffer, size_t size)
 }
 
 
+#ifdef __NVCOMPILER
+#	pragma routine novector
+#endif
 static lzma_ret
 delta_decode(void *coder_ptr, const lzma_allocator *allocator,
 		const uint8_t *restrict in, size_t *restrict in_pos,