Fix mmg_get_tagname test case compilation when USE_ELAS is OFF and US… #631

Job	Run time
mmg-debug / ci (ubuntu-20.04, on, off, on, off, int32_t)	1h 15m 34s
mmg-debug / ci (ubuntu-20.04, on, off, off, off, int32_t)	1h 32m 26s
mmg-debug / ci (ubuntu-20.04, off, off, on, off, int32_t)	1h 0m 41s
mmg-debug / ci (ubuntu-20.04, off, off, off, off, int32_t)	1h 11m 52s
mmg-debug / ci (macos-12, on, off, on, off, int32_t)	39m 49s
mmg-debug / ci (macos-12, on, off, off, off, int32_t)	52m 41s
mmg-debug / ci (macos-12, off, off, on, off, int32_t)	33m 13s
mmg-debug / ci (macos-12, off, off, off, off, int32_t)	41m 45s
mmg-debug / ci (ubuntu-20.04, off, off, off, on, int32_t)	4m 30s
mmg-debug / ci (macos-12, off, off, off, on, int32_t)	9m 26s
mmg-debug / ci (ubuntu-20.04, off, on, on, off, int32_t)	1h 0m 20s
mmg-debug / ci (macos-12, off, on, on, off, int32_t)	34m 13s
mmg-debug / ci (windows-2022, off, off, off, off, int32_t)	53m 47s
mmg-debug / ci (windows-2022, on, off, off, off, int32_t)	53m 46s
mmg-debug / ci (windows-2022, off, on, off, off, int32_t)	52m 2s
mmg-debug / ci (ubuntu-20.04, on, on, on, on, int64_t)	4m 54s
mmg-debug / ci (ubuntu-20.04, off, off, on, on, int64_t)	1h 8m 16s
mmg-debug / ci (ubuntu-20.04, off, off, off, off, int64_t)	2m 13s
mmg-debug / ci (macos-12, on, on, on, on, int64_t)	9m 20s
mmg-debug / ci (macos-12, off, off, off, off, int64_t)	5m 9s
mmg-debug / ci (windows-2022, on, on, off, off, int64_t)	4m 43s
mmg-debug / ci (windows-2022, off, off, off, off, int64_t)	4m 3s
mmg-debug / upload_coverage	1m 36s
	13h 56m 19s

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