build: rework x86 CPU variants

Type: improvement
Change-Id: Ief243f88e654e578ef9b8060fcf535b364aececb
Signed-off-by: Damjan Marion <damarion@cisco.com>

extras/rpm/vpp.spec

@@ -68,7 +68,7 @@ BuildRequires: mbedtls-devel mbedtls
 BuildREquires: openssl-devel
 BuildRequires: python36-devel
 %if 0%{rhel} == 7
-BuildRequires: devtoolset-7-toolchain
+BuildRequires: devtoolset-9-toolchain
 BuildRequires: cmake3
 BuildRequires: glibc-static, yum-utils
 %else
@@ -177,7 +177,7 @@ groupadd -f -r vpp
 
 %build
 %if 0%{rhel} < 8
-. /opt/rh/devtoolset-7/enable
+. /opt/rh/devtoolset-9/enable
 %endif
 %if %{with aesni}
     make bootstrap