static-build: move all patches to patches sub-directory

We're going to add a whole bunch of them. Putting them all in
a sub-directory will help keeping the file tree organized.

Note, we have to update .gitignore so that the patches/ sub-directory
is ignored only at the top level (it's used by quilt).

NO_DOC=build
NO_TEST=build
NO_CHANGELOG=build

(cherry picked from commit b8ec809e)

.gitignore

@@ -6,7 +6,7 @@ _CPack_Packages
 *.gcno
 *.gcda
 *.gcov
-patches/
+/patches/
 .git-ignore/
 .pc/
 coverity/

static-build/cmake/AddDependencyProjects.cmake

@@ -50,6 +50,8 @@ set(DEPENDENCY_LDFLAGS "${DEPENDENCY_LDFLAGS} ${HARDENING_LDFLAGS}")
 set(DEPENDENCY_CFLAGS "${DEPENDENCY_CFLAGS} ${PREFIX_MAP_FLAGS}")
 set(DEPENDENCY_CXXFLAGS "${DEPENDENCY_CXXFLAGS} ${PREFIX_MAP_FLAGS}")
 
+set(PATCHES_DIR "${CMAKE_CURRENT_LIST_DIR}/../patches")
+
 # Install all libraries required by tarantool at current build dir
 
 #
@@ -73,7 +75,7 @@ ExternalProject_Add(openssl
         no-shared
     INSTALL_COMMAND ${CMAKE_MAKE_PROGRAM} install_sw
     PATCH_COMMAND patch -d <SOURCE_DIR> -p1 <
-        "${CMAKE_CURRENT_LIST_DIR}/../openssl-111q-gh-18720.patch"
+        "${PATCHES_DIR}/openssl-111q-gh-18720.patch"
 )
 set(TARANTOOL_DEPENDS openssl ${TARANTOOL_DEPENDS})
 
@@ -184,7 +186,7 @@ ExternalProject_Add(readline
         --prefix=<INSTALL_DIR>
         --disable-shared
     PATCH_COMMAND patch -d <SOURCE_DIR> -p0 <
-        "${CMAKE_CURRENT_LIST_DIR}/../readline80-001.patch"
+        "${PATCHES_DIR}/readline80-001.patch"
 )
 set(TARANTOOL_DEPENDS readline ${TARANTOOL_DEPENDS})