Add ARDUINO_ARCH_XXX to allow meaningful architecture guards

Author: facchinm

libraries/PDM/library.properties

@@ -6,4 +6,4 @@ sentence=Enables the communication with devices that use the PDM Bus. Specific i
 paragraph=
 category=Communication
 url=
-architectures=nRF52
+architectures=mbed

libraries/PDM/src/PDM.cpp

@@ -1,6 +1,5 @@
-#include <hal/nrf_pdm.h>
-
 #include "PDM.h"
+#include <hal/nrf_pdm.h>
 
 #define DEFAULT_PDM_GAIN     20
 #define PDM_IRQ_PRIORITY     7

libraries/PDM/src/PDM.h

@@ -3,6 +3,10 @@
 
 #include <Arduino.h>
 
+#ifndef ARDUINO_ARCH_NRF52840
+#error "This library targets only NRF52840 boards, not every mbed target"
+#endif
+
 #include "utility/PDMDoubleBuffer.h"
 
 class PDMClass

platform.txt

@@ -18,12 +18,12 @@ compiler.warning_flags.all=-Wall -Wextra
 
 compiler.path={build.compiler_path}
 compiler.c.cmd={build.crossprefix}gcc
-compiler.c.flags=-c -I. {compiler.warning_flags} -Os -g -nostdlib "@{compiler.mbed.defines}" "@{compiler.mbed.cflags}" -MMD -mcpu={build.mcu}
+compiler.c.flags=-c -I. {compiler.warning_flags} -Os -g -nostdlib "@{compiler.mbed.defines}" "@{compiler.mbed.cflags}" {compiler.mbed.arch.define} -MMD -mcpu={build.mcu}
 compiler.c.elf.cmd={build.crossprefix}g++
 compiler.c.elf.flags=-Wl,--gc-sections {compiler.warning_flags} -Wl,--as-needed
 compiler.S.flags=-c -g -x assembler-with-cpp -Os -mcpu={build.mcu}
 compiler.cpp.cmd={build.crossprefix}g++
-compiler.cpp.flags=-c -I. {compiler.warning_flags} -g -Os -nostdlib "@{compiler.mbed.defines}" "@{compiler.mbed.cxxflags}" -MMD -mcpu={build.mcu}
+compiler.cpp.flags=-c -I. {compiler.warning_flags} -g -Os -nostdlib "@{compiler.mbed.defines}" "@{compiler.mbed.cxxflags}" {compiler.mbed.arch.define} -MMD -mcpu={build.mcu}
 compiler.ar.cmd={build.crossprefix}ar
 compiler.ar.flags=rcs
 compiler.objcopy.cmd=