appveyor: Reduce runtime by using lld instead of ld

In particular with the 2019 image, the time required often exceeded the
maximum of 60 minutes.  Using lld reduces the runtime quite a bit (it's
still close to the limit, though).

This doesn't work with the old OpenSSL version we use with the 2015
image (that libeay32.lib file just doesn't seem to work), so continue
to use ld (the build on that image is the quickest anyway).

.appveyor.yml

@@ -29,6 +29,8 @@ install:
       IF "%IMG%" == "2017" set OPENSSL=OpenSSL-v11
       set OPENSSL_DIR=/c/%OPENSSL%-%TEST%
       C:\%OPENSSL%-%TEST%\bin\openssl.exe version -a
+  # lld doesn't read .lib files
+  - IF NOT "%IMG%" == "2015" copy C:\%OPENSSL%-%TEST%\lib\libcrypto.lib C:\%OPENSSL%-%TEST%\lib\libcrypto.dll.a
   # newer versions of msys2 don't provide autotools or gperf via base-devel anymore
   - IF "%IMG%" == "2019" %MSYS_SH% --login -c ". /etc/profile && pacman --noconfirm -S --needed autotools gperf"
 

scripts/test.sh

@@ -352,7 +352,7 @@ win*)
 	else
 		CONFIG="$CONFIG --enable-openssl"
 		CFLAGS="$CFLAGS -I$OPENSSL_DIR/include"
-		LDFLAGS="-L$OPENSSL_DIR/lib"
+		LDFLAGS="-L$OPENSSL_DIR/lib -fuse-ld=lld"
 		case "$IMG" in
 		2015)
 			# gcc/ld might be too old to find libeay32 via .lib instead of .dll
@@ -543,7 +543,7 @@ apidoc)
 	;;
 esac
 
-echo "$ make $TARGET"
+echo "$ make -j$(nproc) $TARGET"
 case "$TEST" in
 sonarcloud)
 	# without target, coverage is currently not supported anyway because