Fix misused tabs in Makefiles

[SharzyL]

Makefile use tabs to identify the lines of recipes. If using tabs in a non-recipe part, it may complain ‘recipe commences before first target. Stop. (Makefile manual) and quits.

[haitaohuang]

You need add Signed-off-by tag in commit. See CONTRIBUTING.md
Also please add the version of make and info of OS on which you encountered the error.

[SharzyL]

The error do not occur in ordinary build process since the problematic corresponding branch is not triggered. But we can manually trigger it by

$ make ARCH=whatever USE_CRYPTO_LIB=0 clean
make[1]: Entering directory '/linux-sgx/sdk'
make -C tlibc/                              clean
make[2]: Entering directory '/linux-sgx/sdk/tlibc'
make[2]: Leaving directory '/linux-sgx/sdk/tlibc'
make -C tlibthread/                         clean
make[2]: Entering directory '/linux-sgx/sdk/tlibthread'
make[2]: Leaving directory '/linux-sgx/sdk/tlibthread'
make -C compiler-rt/                        clean
make[2]: Entering directory '/linux-sgx/sdk/compiler-rt'
make[2]: Leaving directory '/linux-sgx/sdk/compiler-rt'
make -C cpprt                               clean
make[2]: Entering directory '/linux-sgx/sdk/cpprt'
make[2]: Leaving directory '/linux-sgx/sdk/cpprt'
make -C tlibcxx/                            clean
make[2]: Entering directory '/linux-sgx/sdk/tlibcxx'
make[2]: Leaving directory '/linux-sgx/sdk/tlibcxx'
make -C tseal/linux/                        clean
make[2]: Entering directory '/linux-sgx/sdk/tseal/linux'
make[2]: Leaving directory '/linux-sgx/sdk/tseal/linux'
make -C selib/linux/                        clean
make[2]: Entering directory '/linux-sgx/sdk/selib/linux'
make[2]: Leaving directory '/linux-sgx/sdk/selib/linux'
make -C trts/                               clean
make[2]: Entering directory '/linux-sgx/sdk/trts'
make -C linux clean
make[3]: Entering directory '/linux-sgx/sdk/trts/linux'
make[4]: Entering directory '/linux-sgx/external/sgx-emm'
make[4]: Leaving directory '/linux-sgx/external/sgx-emm'
make[3]: Leaving directory '/linux-sgx/sdk/trts/linux'
make[2]: Leaving directory '/linux-sgx/sdk/trts'
make -C tsetjmp/                            clean
make[2]: Entering directory '/linux-sgx/sdk/tsetjmp'
make[2]: Leaving directory '/linux-sgx/sdk/tsetjmp'
make -C tsafecrt/                           clean
make[2]: Entering directory '/linux-sgx/sdk/tsafecrt'
make[2]: Leaving directory '/linux-sgx/sdk/tsafecrt'
make -C gperftools/                         clean
make[2]: Entering directory '/linux-sgx/sdk/gperftools'
make[2]: Leaving directory '/linux-sgx/sdk/gperftools'
make -C tlibcrypto/                         clean
make[2]: Entering directory '/linux-sgx/sdk/tlibcrypto'
Makefile:49: *** recipe commences before first target.  Stop.
make[2]: Leaving directory '/linux-sgx/sdk/tlibcrypto'
make[1]: *** [Makefile.source:326: clean] Error 2
make[1]: Leaving directory '/linux-sgx/sdk'
make: *** [Makefile:483: clean] Error 2

The root cause for it is that make will treat every line begin with a tab as a recipe. Here is a minimum example showing how the error occurs:

# content of Makefile
ifeq (,)
	$(info hello)  # note that this line begins with a tab
endif

default:
	touch defaut

$ make
Makefile:2: *** recipe commences before first target.  Stop.

I can reproduce this error on ubuntu latest, with make 4.3 and commit 05851b2.

[SharzyL]

Rebased and signed off the commit now.

[haitaohuang]

Looks good to me.
Thanks