platform: use lt library for cavs shared sources

Wraps common code into libtool convinence libs, because we don't want to list
common source files for each platform with relative paths.

Signed-off-by: Janusz Jankowski <janusz.jankowski@linux.intel.com>
diff --git a/src/arch/xtensa/Makefile.am b/src/arch/xtensa/Makefile.am
index c37182b..ffe3791 100644
--- a/src/arch/xtensa/Makefile.am
+++ b/src/arch/xtensa/Makefile.am
@@ -87,7 +87,7 @@
 	../../init/libinit.a \
 	../../tasks/libtasks.a \
 	../../lib/libcore.a \
-	../../platform/$(PLATFORM)/libplatform.a \
+	../../platform/$(PLATFORM)/libplatform.la \
 	../../ipc/libsof_ipc.a \
 	../../lib/libdma.a \
 	../../audio/libaudio.a \
diff --git a/src/platform/apollolake/Makefile.am b/src/platform/apollolake/Makefile.am
index ae75353..8b4a9a1 100644
--- a/src/platform/apollolake/Makefile.am
+++ b/src/platform/apollolake/Makefile.am
@@ -4,26 +4,19 @@
 	apollolake.x.in \
 	boot_ldr.x.in
 
-noinst_LIBRARIES = libplatform.a
+noinst_LTLIBRARIES = libplatform.la
 
-libplatform_a_SOURCES = \
-	../intel/cavs/platform.c \
-	../intel/cavs/dai.c \
-	../intel/cavs/dma.c \
-	../intel/cavs/clk.c \
-	../intel/cavs/timer.c \
-	../intel/cavs/interrupt.c \
-	../intel/cavs/memory.c \
-	../intel/cavs/pm_runtime.c \
-	power_down.S
+libplatform_la_LIBADD = ../intel/cavs/libcavsplatform.la
 
-libplatform_a_CFLAGS = \
+libplatform_la_SOURCES = power_down.S
+
+libplatform_la_CFLAGS = \
 	$(ARCH_CFLAGS) \
 	$(ARCH_INCDIR) \
 	$(PLATFORM_INCDIR) \
 	$(SOF_INCDIR)
 
-libplatform_a_CCASFLAGS = \
+libplatform_la_CCASFLAGS = \
 	$(ARCH_INCDIR) \
 	$(ASFLAGS) \
 	$(ARCH_ASFLAGS) \
diff --git a/src/platform/baytrail/Makefile.am b/src/platform/baytrail/Makefile.am
index 03e9c2d..f078609 100644
--- a/src/platform/baytrail/Makefile.am
+++ b/src/platform/baytrail/Makefile.am
@@ -2,9 +2,9 @@
 
 EXTRA_DIST = baytrail.x.in
 
-noinst_LIBRARIES = libplatform.a
+noinst_LTLIBRARIES = libplatform.la
 
-libplatform_a_SOURCES = \
+libplatform_la_SOURCES = \
 	platform.c \
 	dai.c \
 	dma.c \
@@ -12,7 +12,7 @@
 	timer.c \
 	memory.c
 
-libplatform_a_CFLAGS = \
+libplatform_la_CFLAGS = \
 	$(ARCH_CFLAGS) \
 	$(ARCH_INCDIR) \
 	$(PLATFORM_INCDIR) \
diff --git a/src/platform/cannonlake/Makefile.am b/src/platform/cannonlake/Makefile.am
index f9c273a..d7a1e52 100644
--- a/src/platform/cannonlake/Makefile.am
+++ b/src/platform/cannonlake/Makefile.am
@@ -4,19 +4,13 @@
 	cannonlake.x.in \
 	boot_ldr.x.in
 
-noinst_LIBRARIES = libplatform.a
+noinst_LTLIBRARIES = libplatform.la
 
-libplatform_a_SOURCES = \
-	../intel/cavs/platform.c \
-	../intel/cavs/dai.c \
-	../intel/cavs/dma.c \
-	../intel/cavs/clk.c \
-	../intel/cavs/timer.c \
-	../intel/cavs/interrupt.c \
-	../intel/cavs/memory.c \
-	../intel/cavs/pm_runtime.c
+libplatform_la_LIBADD = ../intel/cavs/libcavsplatform.la
 
-libplatform_a_CFLAGS = \
+libplatform_la_SOURCES =
+
+libplatform_la_CFLAGS = \
 	$(ARCH_CFLAGS) \
 	$(ARCH_INCDIR) \
 	$(PLATFORM_INCDIR) \
diff --git a/src/platform/haswell/Makefile.am b/src/platform/haswell/Makefile.am
index 0bb95b2..8e0f221 100644
--- a/src/platform/haswell/Makefile.am
+++ b/src/platform/haswell/Makefile.am
@@ -2,9 +2,9 @@
 
 EXTRA_DIST = haswell.x.in
 
-noinst_LIBRARIES = libplatform.a
+noinst_LTLIBRARIES = libplatform.la
 
-libplatform_a_SOURCES = \
+libplatform_la_SOURCES = \
 	platform.c \
 	dai.c \
 	dma.c \
@@ -12,7 +12,7 @@
 	timer.c \
 	memory.c
 
-libplatform_a_CFLAGS = \
+libplatform_la_CFLAGS = \
 	$(ARCH_CFLAGS) \
 	$(ARCH_INCDIR) \
 	$(PLATFORM_INCDIR) \
diff --git a/src/platform/intel/cavs/Makefile.am b/src/platform/intel/cavs/Makefile.am
index e69de29..503d604 100644
--- a/src/platform/intel/cavs/Makefile.am
+++ b/src/platform/intel/cavs/Makefile.am
@@ -0,0 +1,18 @@
+noinst_LTLIBRARIES = libcavsplatform.la
+
+libcavsplatform_la_SOURCES = \
+	platform.c \
+	dai.c \
+	dma.c \
+	clk.c \
+	timer.c \
+	interrupt.c \
+	memory.c \
+	pm_runtime.c
+
+libcavsplatform_la_CFLAGS = \
+	$(AM_CFLAGS) \
+	$(ARCH_CFLAGS) \
+	$(ARCH_INCDIR) \
+	$(PLATFORM_INCDIR) \
+	$(SOF_INCDIR)