selftests/x86: Detect -no-pie availability

Some toolchains need -no-pie to build all tests, others do not support
the -no-pie flag at all. Therefore, add another test for the
availability of the flag.

This amends commit 3346a6a4e5ba8c040360f753b26938cec31a4bdc
("selftests: x86: sysret_ss_attrs doesn't build on a PIE build").

Signed-off-by: Florian Weimer <[e-mail]>
Acked-by: Randy Dunlap <[e-mail]>
Tested-by: Randy Dunlap <[e-mail]>
Signed-off-by: Shuah Khan (Samsung OSG) <[e-mail]>

tools/testing/selftests/x86/Makefile

···
 UNAME_M := $(shell uname -m)
 CAN_BUILD_I386 := $(shell ./check_cc.sh $(CC) trivial_32bit_program.c -m32)
 CAN_BUILD_X86_64 := $(shell ./check_cc.sh $(CC) trivial_64bit_program.c)
+CAN_BUILD_WITH_NOPIE := $(shell ./check_cc.sh $(CC) trivial_program.c -no-pie)
 
 TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt test_mremap_vdso \
 			check_initial_reg_state sigreturn iopl mpx-mini-test ioperm \
···
 BINARIES_32 := $(patsubst %,$(OUTPUT)/%,$(BINARIES_32))
 BINARIES_64 := $(patsubst %,$(OUTPUT)/%,$(BINARIES_64))
 
-CFLAGS := -O2 -g -std=gnu99 -pthread -Wall -no-pie
+CFLAGS := -O2 -g -std=gnu99 -pthread -Wall
+
+# call32_from_64 in thunks.S uses absolute addresses.
+ifeq ($(CAN_BUILD_WITH_NOPIE),1)
+CFLAGS += -no-pie
+endif
 
 define gen-target-rule-32
 $(1) $(1)_32: $(OUTPUT)/$(1)_32

tools/testing/selftests/x86/trivial_program.c

···
+/* Trivial program to check that compilation with certain flags is working. */
+
+#include <stdio.h>
+
+int
+main(void)
+{
+	puts("");
+	return 0;
+}