Add support for static-only build

Instead of unconditionally building shared libraries, this patch
improves the libsepol build system with a "STATIC" variable, which
when defined to some non-empty value, will disable the build of shared
libraries. It allows to support cases where the target architecture
does not have support for shared libraries.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Adam Duskett <Aduskett@gmail.com>

Index: b/src/Makefile
===================================================================

diff --git a/src/Makefile b/src/Makefile
index db6c2ba..0006285 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -30,8 +30,12 @@ LOBJS += $(sort $(patsubst %.c,%.lo,$(wildcard $(CILDIR)/src/*.c) $(CIL_GENERATE
 override CFLAGS += -I$(CILDIR)/include
 endif
 
+ALL_TARGETS = $(LIBA) $(LIBPC)
+ifeq ($(STATIC),)
+ALL_TARGETS += $(LIBSO)
+endif

-all: $(LIBA) $(LIBSO) $(LIBPC)
+all: $(ALL_TARGETS)
 

 $(LIBA):  $(OBJS)
@@ -70,7 +74,11 @@ install: all
 	install -m 755 $(LIBSO) $(SHLIBDIR)
 	test -d $(LIBDIR)/pkgconfig || install -m 755 -d $(LIBDIR)/pkgconfig
 	install -m 644 $(LIBPC) $(LIBDIR)/pkgconfig
+ifeq ($(STATIC),)
+	test -d $(SHLIBDIR) || install -m 755 -d $(SHLIBDIR)
+	install -m 755 $(LIBSO) $(SHLIBDIR)
 	ln -sf --relative $(SHLIBDIR)/$(LIBSO) $(LIBDIR)/$(TARGET)
+endif
 
 relabel:
 	/sbin/restorecon $(SHLIBDIR)/$(LIBSO)