Update libfuzzer to LLVM 18 #984

Job	Run time
Test (bloaty_fuzz_target)	15m 23s
Test (bloaty_fuzz_target_52948c)	18m 37s
Test (curl_curl_fuzzer_http)	15m 41s
Test (freetype2_ftfuzzer)	13m 10s
Test (harfbuzz_hb-shape-fuzzer)	14m 7s
Test (harfbuzz_hb-shape-fuzzer_17863b)	13m 52s
Test (jsoncpp_jsoncpp_fuzzer)	12m 13s
Test (lcms_cms_transform_fuzzer)	12m 55s
Test (libjpeg-turbo_libjpeg_turbo_fuzzer)	12m 54s
Test (libpcap_fuzz_both)	12m 20s
Test (libpng_libpng_read_fuzzer)	12m 8s
Test (libxml2_xml)	12m 35s
Test (libxml2_xml_e85b9b)	12m 29s
Test (libxslt_xpath)	13m 30s
Test (mbedtls_fuzz_dtlsclient)	13m 45s
Test (mbedtls_fuzz_dtlsclient_7c6b0e)	14m 19s
Test (openh264_decoder_fuzzer)	12m 38s
Test (openssl_x509)	14m 40s
Test (openthread_ot-ip6-send-fuzzer)	12m 45s
Test (php_php-fuzz-parser_0dbedb)	18m 12s
Test (proj4_proj_crs_to_crs_fuzzer)	15m 31s
Test (re2_fuzzer)	12m 6s
Test (sqlite3_ossfuzz)	12m 57s
Test (stb_stbi_read_fuzzer)	12m 32s
Test (systemd_fuzz-link-parser)	14m 8s
Test (vorbis_decode_fuzzer)	11m 58s
Test (woff2_convert_woff2ttf_fuzzer)	14m 10s
Test (zlib_zlib_uncompress_fuzzer)	12m 6s
	6h 23m 41s

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