Document how to force linking with static libraries

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1889)

Configurations/README

diff --git a/Configurations/README b/Configurations/README
index 0b82ded..21a6f03 100644
--- a/Configurations/README
+++ b/Configurations/README
@@ -339,6 +339,17 @@
 to be located in the source tree while files given through DEPEND are
 expected to be located in the build tree)
 
+It's also possible to depend on static libraries explicitely:
+
+    DEPEND[foo]=libsomething.a
+    DEPEND[libbar]=libsomethingelse.a
+
+This should be rarely used, and care should be taken to make sure it's
+only used when supported.  For example, native Windows build doesn't
+support build static libraries and DLLs at the same time, so using
+static libraries on Windows can only be done when configured
+'no-shared'.
+
 For some libraries, we maintain files with public symbols and their
 slot in a transfer vector (important on some platforms).  It can be
 declared like this:

Configurations/README.design

diff --git a/Configurations/README.design b/Configurations/README.design
index bea9790..41c2949 100644
--- a/Configurations/README.design
+++ b/Configurations/README.design
@@ -133,7 +133,7 @@
 
     ENGINES_NO_INST=ossltest
     SOURCE[ossltest]=e_ossltest.c
-    DEPEND[ossltest]=../libcrypto
+    DEPEND[ossltest]=../libcrypto.a
     INCLUDE[ossltest]=../include
 
 This is the build.info file in 'engines/', telling us that two engines
@@ -142,8 +142,9 @@
 'engines/e_ossltest.c' and that the include directory 'include/' may
 be used when building anything that will be part of these engines.
 Also, both engines depend on the library 'libcrypto' to function
-properly.  Finally, only dasync is being installed, as ossltest is
-only for internal testing.
+properly.  ossltest is explicitly linked with the static variant of
+the library 'libcrypto'.  Finally, only dasync is being installed, as
+ossltest is only for internal testing.
 
 When Configure digests these build.info files, the accumulated
 information comes down to this:
@@ -170,7 +171,7 @@
 
     ENGINES_NO_INST=engines/ossltest
     SOURCE[engines/ossltest]=engines/e_ossltest.c
-    DEPEND[engines/ossltest]=libcrypto
+    DEPEND[engines/ossltest]=libcrypto.a
     INCLUDE[engines/ossltest]=include
     
     GENERATE[crypto/buildinf.h]=util/mkbuildinf.pl "$(CC) $(CFLAGS)" "$(PLATFORM)"
@@ -281,10 +282,14 @@
                     [
                         "crypto/buildinf.h",
                     ],
-                "engines/ossltest" =>
+                "engines/dasync" =>
                     [
                         "libcrypto",
                     ],
+                "engines/ossltest" =>
+                    [
+                        "libcrypto.a",
+                    ],
                 "libssl" =>
                     [
                         "libcrypto",
@@ -396,6 +401,14 @@
                     [
                         "crypto/evp.c",
                     ],
+                "engines/e_dasync.o" =>
+                    [
+                        "engines/e_dasync.c",
+                    ],
+                "engines/dasync" =>
+                    [
+                        "engines/e_dasync.o",
+                    ],
                 "engines/e_ossltest.o" =>
                     [
                         "engines/e_ossltest.c",