mbedtls: build with PIC

Fixes compilation with GCC12 and dependent packages for some reason.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

package/libs/mbedtls/Makefile

@@ -91,6 +91,7 @@ TARGET_CFLAGS += -ffunction-sections -fdata-sections
 TARGET_CFLAGS := $(filter-out -O%,$(TARGET_CFLAGS))
 
 CMAKE_OPTIONS += \
+	-DCMAKE_POSITION_INDEPENDENT_CODE=ON \
 	-DUSE_SHARED_MBEDTLS_LIBRARY:Bool=ON \
 	-DENABLE_TESTING:Bool=OFF \
 	-DENABLE_PROGRAMS:Bool=ON