Disable all sha1 by default #356

Job	Run time
build (plain linux, 1)	1m 16s
build (multi binary, 1, 1)	1m 46s
build (multi binary, dropbearmulti argv0, 1, 1)	1m 58s
build (client only, no, PROGRAMS=dbclient)	22s
build (server only, no, PROGRAMS=dropbear)	51s
build (bundled libtom, bionic , no writev(), ubuntu-20.04, --enable-bundled-libtom --enable-werro...	37s
build (linux clang, clang)	4m 56s
build (c89, -std=c89 -Wdeclaration-after-statement, 1, --enable-pam, #define DROPBEAR_SNTRUP761 0 )	57s
build (macos 14, macos-14, clang, -Wno-deprecated-declarations -Wno-undef, no, no, ranlib -no_war...	34s
build (macos 15, macos-15, clang, -Wno-deprecated-declarations -Wno-undef, no, no, ranlib -no_war...	36s
build (DEBUG_TRACE, 1, --enable-pam, #define DEBUG_TRACE 5 )	1m 47s
build (nondefault options, 1, --enable-pam)	1m 35s
build (most options disabled, --disable-harden --disable-zlib --disable-openpty --disable-lastlog...	44s
build (no sha1, no, #define DROPBEAR_SHA1_HMAC 0 #define DROPBEAR_RSA_SHA1 0 #define DROPBEAR_DH_...	23s
build (pq, no plain x25519, #define DROPBEAR_CURVE25519 0 )	1m 30s
	19m 52s

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