build: require gcc >= 9.1, recommend gcc >= 10.2

Similarly, recommend clang 10 or later. On macOS, the minimum Xcode
version is now 11, the recommended one is still 13 or later.

Also remove unnecessary dependency on libboost-filesystem.

Change-Id: I79eb1c018dcffeb272589f4a027bf7c90fd47521
diff --git a/.jenkins.d/00-deps.sh b/.jenkins.d/00-deps.sh
index c20d217..3f3235a 100755
--- a/.jenkins.d/00-deps.sh
+++ b/.jenkins.d/00-deps.sh
@@ -7,7 +7,6 @@
     libboost-chrono-dev
     libboost-date-time-dev
     libboost-dev
-    libboost-filesystem-dev
     libboost-iostreams-dev
     libboost-log-dev
     libboost-program-options-dev
@@ -19,7 +18,7 @@
     pkg-config
     python3
 )
-FORMULAE=(boost openssl pkg-config)
+FORMULAE=(boost openssl pkgconf)
 PIP_PKGS=()
 case $JOB_NAME in
     *code-coverage)