DOC: install: update quick build reminders with some missing options

The quick build reminders claimed to present "all options" but were
still missing QUIC. It was also the moment to split FreeBSD and
OpenBSD apart since the latter uses LibreSSL and does not require
the openssl compatibility wrapper. We also replace the hard-coded
number of cpus for the parallel build, by the real number reported
by the system.

INSTALL

@@ -34,18 +34,26 @@ are a few build examples :
   - recent Linux system with all options, make and install :
     $ make clean
     $ make -j $(nproc) TARGET=linux-glibc \
-                USE_OPENSSL=1 USE_LUA=1 USE_PCRE2=1 USE_SYSTEMD=1
+           USE_OPENSSL=1 USE_QUIC=1 USE_QUIC_OPENSSL_COMPAT=1 \
+           USE_LUA=1 USE_PCRE2=1
     $ sudo make install
 
-  - FreeBSD and OpenBSD, build with all options :
-    $ gmake -j 4 TARGET=freebsd USE_OPENSSL=1 USE_LUA=1 USE_PCRE2=1
+  - FreeBSD + OpenSSL, build with all options :
+    $ gmake -j $(sysctl -n hw.ncpu) TARGET=freebsd \
+           USE_OPENSSL=1 USE_QUIC=1 USE_QUIC_OPENSSL_COMPAT=1 \
+           USE_LUA=1 USE_PCRE2=1
+
+  - OpenBSD + LibreSSL, build with all options :
+    $ gmake -j $(sysctl -n hw.ncpu) TARGET=openbsd \
+           USE_OPENSSL=1 USE_QUIC=1 USE_LUA=1 USE_PCRE2=1
 
   - embedded Linux, build using a cross-compiler :
     $ make -j $(nproc) TARGET=linux-glibc USE_OPENSSL=1 USE_PCRE2=1 \
-                CC=/opt/cross/gcc730-arm/bin/gcc ADDLIB=-latomic
+           CC=/opt/cross/gcc730-arm/bin/gcc CFLAGS="-mthumb" ADDLIB=-latomic
 
   - Build with static PCRE on Solaris / UltraSPARC :
-    $ make TARGET=solaris CPU_CFLAGS="-mcpu=v9" USE_STATIC_PCRE2=1
+    $ make -j $(/usr/sbin/psrinfo -p) TARGET=solaris \
+           CPU_CFLAGS="-mcpu=v9" USE_STATIC_PCRE2=1
 
 For more advanced build options or if a command above reports an error, please
 read the following sections.