ci: build stm32mp1-135F_DK with Clang

Adds a build of stm32mp1-135F_DK platform with Clang to ensure
the several driver frameworks enabled by this platform comply
with a Clang build.

Signed-off-by: Etienne Carriere <etienne.carriere@foss.st.com>

.github/workflows/ci.yml

@@ -139,6 +139,7 @@ jobs:
           _make PLATFORM=stm-cannes
           _make PLATFORM=stm32mp1
           _make PLATFORM=stm32mp1-135F_DK CFG_DRIVERS_CLK_PRINT_TREE=y
+          _make PLATFORM=stm32mp1-135F_DK COMPILER=clang
           if [ -d $HOME/scp-firmware ]; then _make PLATFORM=stm32mp1-157C_DK2 CFG_SCMI_SCPFW=y CFG_SCP_FIRMWARE=$HOME/scp-firmware; fi
           _make PLATFORM=stm32mp2
           _make PLATFORM=vexpress-fvp